TW201431088A - Semiconductor device and method of manufacturing same - Google Patents

Abstract

A semiconductor device with high aperture ratio is provided. The semiconductor device includes a transistor and a capacitor having a pair of electrodes. An oxide semiconductor layer formed over the same insulating surface is used for a channel formation region of the transistor and one of the electrodes of the capacitor. The other electrode of the capacitor is a transparent conductive film. One electrode of the capacitor is electrically connected to a wiring formed over the insulating surface over which a source electrode or a drain electrode of the transistor is provided, and the other electrode of the capacitor is electrically connected to one of the source electrode and the drain electrode of the transistor.

Description

Semiconductor device and method of manufacturing same

The present invention relates to an object, method or method of manufacture. Alternatively, the invention relates to a process, a machine, a manufacture or a composition of matter. For example, the present invention relates in particular to a semiconductor device, a display device, a light emitting device, a driving method of the above device, or a method of manufacturing the above device. For example, the present invention relates in particular to a semiconductor device including an oxide semiconductor, a display device, or a light-emitting device, and a method of fabricating the same.

In recent years, flat panel displays such as liquid crystal displays (LCDs) have been widely spread. In a display device such as a flat panel display, a transistor as a switching element, a liquid crystal element electrically connected to the transistor, and a capacitor element connected in parallel to the liquid crystal element are provided in a pixel arranged in the row direction and the column direction.

As the semiconductor material constituting the semiconductor film of the transistor, a germanium semiconductor such as amorphous germanium or polycrystalline germanium is usually used.

Further, a metal oxide exhibiting semiconductor characteristics (hereinafter also referred to as an oxide semiconductor) is also a semiconductor material which can be used as a semiconductor film of a transistor. For example, a technique for producing a transistor using zinc oxide or an In-Ga-Zn-based oxide semiconductor has been disclosed (see Patent Document 1 and Patent Document 2).

[Patent Document 1] Japanese Patent Application Publication No. 2007-123861

[Patent Document 2] Japanese Patent Application Publication No. 2007-96055

In the capacitor element, a dielectric film is provided between a pair of electrodes, and at least one of the pair of electrodes is formed of the same material as a gate electrode, a source electrode or a gate electrode constituting the transistor, and thus The capacitor element is generally formed of a light-shielding conductive film such as metal.

Further, when an electric field is applied, the capacitance value of the capacitor element is larger, and the period during which the alignment of the liquid crystal molecules of the liquid crystal element is kept constant is longer. In a display device capable of displaying a still image, extending the period means that the number of times of rewriting the image data can be reduced, and power consumption can be reduced.

In order to increase the charge capacity of the capacitor element, the area occupied by the capacitor element in the pixel can be increased, and specifically, the area in which the pair of electrodes overlap each other can be increased. However, in the display device described above, when the area of the light-shielding conductive film is increased in order to increase the area where the pair of electrodes overlap each other, the aperture ratio of the pixel is lowered, and the image display quality is lowered.

In view of the above problems, it is an object of one embodiment of the present invention to provide a semiconductor device or the like having a high aperture ratio. Alternatively, it is an object of one embodiment of the present invention to provide a semiconductor device or the like having a capacitor element capable of increasing a charge capacity. Alternatively, it is an object of one embodiment of the present invention to provide a semiconductor device or the like which can reduce the number of masks in the photolithography process. Alternatively, it is an object of one embodiment of the present invention to provide a semiconductor device or the like having a low off-state current. Alternatively, it is an object of one embodiment of the present invention to provide a semiconductor device or the like which consumes low power. Alternatively, it is an object of one embodiment of the present invention to provide a semiconductor device or the like using a transparent semiconductor layer. Alternatively, it is an object of one embodiment of the present invention to provide a highly reliable semiconductor device or the like. Alternatively, it is an object of one embodiment of the present invention to provide a semiconductor device or the like which is less irritating to the eyes. Alternatively, it is an object of one embodiment of the present invention to provide a novel semiconductor device or the like. Alternatively, it is an object of one embodiment of the present invention to provide a novel semiconductor device or the like.

Note that these purposes do not prevent the existence of other purposes. Moreover, one aspect of the present invention does not need to achieve all of the above objects. In addition, it is known from the descriptions of the specification, the drawings, the patent application scope, and the like that the above objects can be extracted.

One aspect of the present invention relates to a semiconductor device including a light-transmitting capacitive element which uses an oxide semiconductor layer as one electrode and a light-transmitting conductive film as another electrode.

One aspect of the present invention is a semiconductor device having a transistor, comprising: a first oxide semiconductor layer and a second oxide semiconductor layer formed on a first insulating film; and a source electrically connected to the first oxide semiconductor layer An electrode layer and a drain electrode layer; a wiring electrically connected to the second oxide semiconductor layer; a first insulating film, a first oxide semiconductor layer, a second oxide semiconductor layer, a source electrode layer, and a drain electrode layer And a second insulating film on the wiring; a gate electrode layer overlapping the first oxide semiconductor layer via the second insulating film; a third insulating film formed on the second insulating film and the gate electrode layer; a fourth insulating film on the third insulating film; and a light-transmitting conductive film formed on the second oxide semiconductor layer and formed on the fourth insulating film, further including a capacitor element in which the second oxide is The semiconductor layer functions as one electrode; the second insulating film, the third insulating film, and the fourth insulating film are used as a dielectric; and the light-transmitting conductive film is used as the other electrode.

The first oxide semiconductor layer and the second oxide semiconductor layer are preferably formed using the same material.

Further, the energy gap of the first oxide semiconductor layer and the second oxide semiconductor layer is preferably 2.0 eV or more.

One or more dopants selected from the group consisting of hydrogen, boron, nitrogen, fluorine, aluminum, phosphorus, arsenic, indium, tin, antimony, and rare gas elements may be added to the second oxide semiconductor layer.

The dielectric may be formed of the second insulating film, the third insulating film, and the fourth insulating film.

Further, the dielectric may be formed of the third insulating film and the fourth insulating film.

In addition, a dielectric may be formed of a fourth insulating film.

Further, the third insulating film is preferably formed of a single layer structure or a stacked structure of an oxidized insulating material selected from the group consisting of yttrium oxide, lanthanum oxynitride, aluminum oxide, lanthanum oxide, gallium oxide, and Ga-Zn-based metal oxide. .

Further, the fourth insulating film is preferably formed of a single layer structure or a laminated structure of a nitride insulating material selected from the group consisting of bismuth oxynitride, tantalum nitride, aluminum nitride, and aluminum oxynitride.

Further, a nitride insulating film containing hydrogen may be formed between the first insulating film and the second oxide semiconductor layer.

Further, the source electrode layer, the gate electrode layer, and the wiring may have a structure formed on the same insulating surface.

Further, the source electrode layer, the gate electrode layer, and the wiring may be formed using the same material.

In addition, the light-transmitting conductive film may have a structure electrically connected to one of the source electrode and the drain electrode.

Further, another aspect of the present invention is a method of fabricating a semiconductor device, comprising the steps of: forming a first oxide semiconductor layer and a second oxide semiconductor layer on a first insulating film; forming a first oxide semiconductor layer a connected source electrode layer and a drain electrode layer, and a wiring electrically connected to the second oxide semiconductor layer; and a first insulating film, a first oxide semiconductor layer, a second oxide semiconductor layer, a source electrode layer, and a drain a second insulating film is formed on the electrode layer and the wiring; a gate electrode layer overlapping the first oxide semiconductor layer is formed on the second insulating film; and a third insulating film is formed on the second insulating film and the gate electrode layer; Forming a fourth insulation on the third insulating film a film; an opening reaching the source electrode layer or the drain electrode layer is formed in the second insulating film, the third insulating film, and the fourth insulating film; and the opening portion and the source electrode layer or the germanium are formed on the fourth insulating film a light-transmissive conductive film electrically connected to the electrode layer to form a transistor and a capacitor element, the capacitor element including a second oxide semiconductor layer serving as one electrode, a light-transmitting conductive film serving as another electrode, and being used as a dielectric a second insulating film, a third insulating film, and a fourth insulating film.

It is preferable to form the first oxide semiconductor layer and the second oxide semiconductor layer using the same material.

Further, it is preferable to form the first oxide semiconductor layer and the second oxide semiconductor layer using a material having an energy gap of 2.0 eV or more.

Further, a dopant selected from the group consisting of hydrogen, boron, nitrogen, fluorine, aluminum, phosphorus, arsenic, indium, tin, antimony, and a rare gas element may be added to the second oxide semiconductor layer.

The dielectric may be formed of the second insulating film, the third insulating film, and the fourth insulating film.

Further, the second insulating film on the second oxide semiconductor layer may be etched, and the dielectric material may be formed of the third insulating film and the fourth insulating film.

Further, the second insulating film and the third insulating film on the second oxide semiconductor layer may be etched, and the dielectric material may be formed of the fourth insulating film.

Further, it is preferably oxidized in a metal oxide selected from the group consisting of cerium oxide, cerium oxynitride, aluminum oxide, cerium oxide, gallium oxide or Ga-Zn metal oxide. The single layer structure or the laminated structure of the edge material forms a third insulating film.

Further, it is preferable that the fourth insulating film is formed in a single layer structure or a stacked structure of a nitride insulating material selected from the group consisting of bismuth oxynitride, tantalum nitride, aluminum nitride, and aluminum oxynitride.

Further, a nitride insulating film containing hydrogen may be formed between the first insulating film and the second oxide semiconductor layer.

Further, it is preferable to form the source electrode layer, the gate electrode layer, and the wiring using the same material.

Further, it is preferable that the source electrode layer, the gate electrode layer, and the wiring are formed on the same insulating surface.

According to an aspect of the present invention, a semiconductor device or the like having a high aperture ratio can be provided. Alternatively, a semiconductor device or the like having a capacitance element capable of increasing a charge capacity can be provided. Alternatively, a semiconductor device or the like capable of reducing the number of masks for the photolithography process can be provided. Alternatively, a semiconductor device or the like having a low off-state current can be provided. Alternatively, a semiconductor device or the like having a low power consumption can be provided. Alternatively, a semiconductor device or the like using a transparent semiconductor layer can be provided. Alternatively, a highly reliable semiconductor device or the like can be provided. Alternatively, a semiconductor device that is less irritating to the eyes can be provided. Alternatively, a method of manufacturing a semiconductor device or the like can be provided.

100‧‧‧Pixel Department

101‧‧ ‧ pixels

102‧‧‧Substrate

103‧‧‧Optoelectronics

104‧‧‧ drive circuit

105‧‧‧Capacitive components

106‧‧‧Drive circuit

107‧‧‧ scan line

108‧‧‧Liquid components

109‧‧‧ signal line

110‧‧‧Base insulating film

111‧‧‧Semiconductor film

113‧‧‧Electrical film

115‧‧‧ capacitance line

117‧‧‧ openings

118‧‧‧Nitrided insulating film

119‧‧‧Semiconductor film

121‧‧‧pixel electrode

127‧‧‧gate insulating film

129‧‧‧Insulation film

130‧‧‧Insulation film

131‧‧‧Insulation film

132‧‧‧Insulation film

135‧‧‧ border

154‧‧‧ counter electrode

188a‧‧‧Oxide semiconductor film

188b‧‧‧Oxide semiconductor film

199a‧‧‧Oxide semiconductor film

199b‧‧‧Oxide semiconductor film

199c‧‧‧Oxide semiconductor film

223‧‧‧Optoelectronics

227‧‧‧gate electrode

229‧‧‧Wiring

231‧‧‧Semiconductor film

233‧‧‧Wiring

241‧‧‧Electrical film

310‧‧‧Arithmetic device

311‧‧‧ Computing Department

312‧‧‧ Memory Department

314‧‧‧Transmission channel

315‧‧‧Input and output interface

320‧‧‧Input and output devices

321‧‧‧ input unit

322‧‧‧Display Department

330‧‧‧Information processing device

500‧‧‧ input unit

500_C‧‧‧ signal

600‧‧‧Information processing device

610‧‧‧Control Department

615_C‧‧‧ secondary control signal

615_V‧‧‧ secondary image signal

620‧‧‧Arithmetic device

625_C‧‧‧One control signal

625_V‧‧‧One image signal

630‧‧‧Display Department

631‧‧‧Pixel Department

631a‧‧‧Area

631b‧‧‧Area

631c‧‧‧Area

631p‧‧ ‧ pixels

632‧‧‧G drive circuit

632_G‧‧‧G signal

632a‧‧‧G drive circuit

632b‧‧‧G drive circuit

632c‧‧‧G drive circuit

633‧‧‧S drive circuit

633_S‧‧‧S signal

634‧‧‧pixel circuit

634c‧‧‧Capacitive components

634EL‧‧‧pixel circuit

634t‧‧‧Optoelectronics

634t_1‧‧‧Optoelectronics

634t_2‧‧‧Optoelectronics

635‧‧‧Display components

635EL‧‧‧EL components

635LC‧‧‧Liquid Crystal Components

640‧‧‧ display device

650‧‧‧Light Supply Department

701‧‧‧ Computing Department

702‧‧‧Memory Department

703‧‧‧Control Department

704‧‧‧Display Department

901‧‧‧Substrate

902‧‧‧Pixel Department

903‧‧‧Drive circuit

904‧‧‧Drive circuit

905‧‧‧ Sealing material

906‧‧‧Substrate

908‧‧‧Liquid layer

910‧‧‧Optoelectronics

911‧‧‧Optoelectronics

913‧‧‧Liquid crystal components

915‧‧‧Connecting terminal electrode

916‧‧‧Terminal electrode

917‧‧‧Electrical film

918‧‧‧FPC

918b‧‧‧FPC

919‧‧‧Anisotropic conductive agent

922‧‧‧gate insulating film

923‧‧‧Insulation film

924‧‧‧Insulation film

925‧‧‧ sealing material

926‧‧‧Capacitive components

927‧‧‧Oxide semiconductor film

929‧‧‧ capacitance line

930‧‧‧electrode

931‧‧‧electrode

932‧‧‧Insulation film

933‧‧‧Insulation film

934‧‧‧Insulation film

935‧‧‧ spacers

936‧‧‧Capacitive components

971‧‧‧Source electrode

973‧‧‧汲electrode

975‧‧‧shared potential line

977‧‧‧Common electrode

985‧‧‧ shared potential line

987‧‧‧Common electrode

9000‧‧‧Table

9001‧‧‧ Shell

9002‧‧‧Table legs

9003‧‧‧Display Department

9004‧‧‧Display button

9005‧‧‧Power supply line

9033‧‧‧ clip

9034‧‧‧Switch

9035‧‧‧Power switch

9036‧‧‧ switch

9038‧‧‧Operation switch

9100‧‧‧TV

9101‧‧‧Shell

9103‧‧‧Display Department

9105‧‧‧ bracket

9107‧‧‧Display Department

9109‧‧‧ operation keys

9110‧‧‧Remote control

9200‧‧‧ computer

9201‧‧‧ Subject

9202‧‧‧Shell

9203‧‧‧Display Department

9204‧‧‧ keyboard

9205‧‧‧External connection埠

9206‧‧‧ pointing device

9630‧‧‧Shell

9631‧‧‧Display Department

9631a‧‧‧Display Department

9631b‧‧‧Display Department

9632a‧‧‧Area

9632b‧‧‧Area

9633‧‧‧Solar battery

9634‧‧‧Charge and discharge control circuit

9635‧‧‧Battery

9636‧‧‧DCDC converter

9637‧‧‧DCDC Converter

9638‧‧‧ operation keys

9639‧‧‧ button

In the schema: 1 is a plan view illustrating a semiconductor device; FIG. 2 is a cross-sectional view illustrating the semiconductor device; FIG. 3 is a view illustrating a semiconductor device; FIGS. 4A and 4B are circuit diagrams illustrating a pixel of the semiconductor device; FIGS. 5A and 5B are diagrams illustrating a semiconductor FIG. 6A and FIG. 7B are cross-sectional views illustrating a method of fabricating a semiconductor device; FIGS. 7A and 7B are cross-sectional views illustrating a capacitor element of the semiconductor device; and FIG. 8 is a cross-sectional view illustrating the semiconductor device; 9A and 9B are cross-sectional views illustrating a semiconductor device; Figs. 10A and 10B are views showing a nanobeam electron diffraction pattern of an oxide semiconductor film; and Figs. 11A and 11B are CPMs showing an oxide semiconductor film. FIG. 12 is a view showing a CPM measurement result of a CAAC-OS film; FIG. 13A is a view showing a cross-sectional TEM image of the oxide semiconductor film; and FIGS. 13B to 13D are diagrams showing an oxide semiconductor film. a diagram of a nanobeam electron diffraction pattern; FIG. 14A shows a planar TEM image of the oxide semiconductor film; FIG. 14B shows a selected area electronic diffraction pattern; and FIGS. 15A to 15C are schematic diagrams showing electron diffraction intensity distribution; 16 shows a nanobeam electron diffraction pattern of a quartz glass substrate; FIG. 17 shows a nanobeam electron diffraction pattern of the oxide semiconductor film; FIGS. 18A and 18B show a cross-sectional TEM image of the oxide semiconductor film; 19 shows the results of X-ray diffraction analysis of the oxide semiconductor film; FIG. 20 shows a cross-sectional TEM image of the CAAC-OS film; FIGS. 21A to 21D show the electronic diffraction pattern of the CAAC-OS film; FIG. 22 shows CAAC - FIG. 23A shows a cross-sectional TEM image of a CAAC-OS film; FIG. 23B shows an X-ray diffraction spectrum; and FIGS. 24A to 24D show an electronic diffraction pattern of a CAAC-OS film; A cross-sectional TEM image of the CAAC-OS film is shown; FIG. 25B shows an X-ray diffraction spectrum; FIGS. 26A to 26D show an electron diffraction pattern of the CAAC-OS film; and FIG. 27A shows a cross-sectional TEM image of the CAAC-OS film. Figure 27B shows an X-ray diffraction spectrum; Figures 28A to 28D show an electronic diffraction pattern of a CAAC-OS film; Figures 29A to 29C are plan views illustrating a semiconductor device; and Figure 30 is a cross-sectional view illustrating the semiconductor device; 31A to 31C are cross-sectional views and plan views illustrating a semiconductor device; and Fig. 32 is a view illustrating information processing with a display function FIG opposing block structure; FIGS. 33A1 to 33B2 are explanatory information processing apparatus of a display unit FIG. 34A and FIG. 34B are block diagrams showing the structure of the information processing apparatus and a schematic diagram for explaining the image data; FIGS. 35A1 to 35B2 are diagrams for explaining the effects of the information processing apparatus; FIG. 36 is a diagram for explaining the information processing. FIG. 37A to FIG. 37C are diagrams illustrating an electronic device using a semiconductor device; FIGS. 38A and 38B are diagrams illustrating an electronic device using the semiconductor device; and FIGS. 39A to 39C are diagrams illustrating an electronic device using the semiconductor device. Figure.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and one of ordinary skill in the art can easily understand the fact that the manner and details of the present invention can be changed into various forms. Further, the present invention should not be construed as being limited to the contents described in the embodiments shown below.

It is noted that in the structures of the present invention described below, the same reference numerals are used to designate the same parts or parts having the same functions, and the repeated description thereof will be omitted. In addition, the same hatching is sometimes used when representing portions having the same function, and no special symbols are attached.

In each of the drawings described in the specification, the size of each structure, the thickness or the area of the film are sometimes exaggerated for the sake of clarity. Therefore, the present invention is not necessarily limited to this scale.

In the present specification and the like, ordinal numerals such as "first" and "second" are added for convenience, and they do not indicate a process sequence or a stacking order. Further, in the present specification and the like, these ordinal numbers do not denote the inherent names of the items used for the specific invention.

In addition, the voltage refers to the potential difference between two points, and the potential refers to the electrostatic energy (potential energy) of the unit charge in the electrostatic field at a certain point. However, in general, the potential difference between a potential at a certain point and a standard potential (for example, a ground potential) is simply referred to as a potential or a voltage. Generally, the potential and voltage are synonymous. Therefore, in the present specification, "potential" may be referred to as "voltage" or "voltage" as "potential" unless otherwise specified.

In the present specification, when the etching process is performed after the photolithography process, the photoresist mask formed in the photolithography process is removed.

Embodiment 1

In the present embodiment, a semiconductor device according to one embodiment of the present invention will be described with reference to the drawings. Further, in the present embodiment, a semiconductor device according to one embodiment of the present invention will be described using a liquid crystal display device as an example. Further, the semiconductor device of one embodiment of the present invention can also be applied to other display devices.

3 is a view showing a semiconductor device of one embodiment of the present invention; Figure. The semiconductor device shown in FIG. 3 includes: a pixel portion 100; a first driving circuit 104; a second driving circuit 106; m scanning lines 107 which are arranged in parallel or substantially parallel to each other and whose potential is controlled by the first driving circuit 104; The n signal lines 109 are arranged parallel or substantially parallel to each other and whose potential is controlled by the second drive circuit 106. The pixel portion 100 further has a plurality of pixels 101 arranged in a matrix. In addition, the semiconductor device includes a capacitor line 115 (not shown in FIG. 3). The capacitance lines 115 are respectively arranged in parallel or substantially parallel along the scanning line 107, or the capacitance lines 115 are respectively arranged in parallel or substantially parallel along the signal lines 109.

Each of the scanning lines 107 is electrically connected to n pixels 101 arranged in any one of the pixels 101 arranged in m rows and n columns in the pixel portion 100. Further, each signal line 109 is electrically connected to m pixels 101 arranged in any one of the pixels 101 arranged in m rows and n columns. Both m and n are integers of 1 or more. In addition, each capacitance line 115 is electrically connected to n pixels 101 arranged in any row among the pixels 101 configured as m rows and n columns. In addition, when the capacitance lines 115 are arranged along the signal lines 109 in a parallel or substantially parallel manner, respectively, they are electrically connected to m pixels 101 arranged in any one of the pixels 101 arranged in m rows and n columns.

In addition, the first driving circuit 104 may have a function of supplying a signal for turning on or off the transistor connected to the scanning line 107, for example, as a scanning line driving circuit. Further, the second driving circuit 106 may have a function of supplying an image signal to a transistor connected to the signal line 109, for example, as a signal line driving circuit. Note that, without being limited thereto, the first driving circuit 104 and the second driving circuit 106 may also supply the same His signal.

Further, in the present embodiment, in order to facilitate the description of the liquid crystal display device as an example, the wiring connected to the first driving circuit 104 is referred to as a scanning line 107 and a capacitance line 115, and the wiring connected to the second driving circuit 106 is referred to as a wiring. It is signal line 109, but its function is not limited by its name.

FIG. 1 is a plan view illustrating a configuration of an example of a pixel 101 included in the semiconductor device. Note that in FIG. 1, one of a pair of electrodes included in the liquid crystal layer and the liquid crystal element is omitted.

In the pixel 101 shown in FIG. 1, the scanning line 107 is provided so as to extend in a direction (row direction) substantially orthogonal to the signal line 109. The signal line 109 is provided so as to extend in a direction (column direction) substantially orthogonal to the scanning line 107. A capacitance line 115 is provided in such a manner as to extend in a direction parallel to the signal line 109. Further, the scanning line 107 is electrically connected to the first driving circuit 104 (see FIG. 3), and the signal line 109 is electrically connected to the second driving circuit 106 (refer to FIG. 3).

The transistor 103 is disposed in the vicinity of a region where the scanning line 107 and the signal line 109 intersect. The transistor 103 includes at least a semiconductor film 111 having a channel formation region, a gate electrode, a gate insulating film (not shown in FIG. 1), a source electrode, and a drain electrode. Further, a region of the scanning line 107 overlapping with the semiconductor film 111 is used as a gate electrode of the transistor 103. A region of the signal line 109 overlapping with the semiconductor film 111 serves as one of the source electrode and the drain electrode of the transistor 103. A region of the conductive film 113 overlapping with the semiconductor film 111 serves as a source electrode and a drain electrode of the transistor 103. The other one. Thus, the gate electrode, the source electrode, and the drain electrode are sometimes referred to as the scanning line 107, the signal line 109, and the conductive film 113, respectively. Further, in the plan view shown in FIG. 1, the edge of the scanning line 107 is located outside the edge of the semiconductor film 111. Therefore, the scanning line 107 functions as a light shielding film that blocks light from the outside. As a result, light is not irradiated onto the semiconductor film 111 included in the transistor, whereby variation in electrical characteristics of the transistor can be suppressed.

Further, in one embodiment of the present invention, an oxide semiconductor is preferably used for the semiconductor film 111. By manufacturing a transistor using an oxide semiconductor by using appropriate conditions, the off-state current can be made extremely small. Therefore, the power consumption of the semiconductor device can be reduced.

In one embodiment of the invention, the transistor using the oxide semiconductor is an n-channel type transistor. Further, oxygen defects contained in the oxide semiconductor sometimes generate carriers, which may lower the electrical characteristics and reliability of the transistor. For example, sometimes the threshold voltage of the transistor fluctuates in the negative direction, causing the drain current to flow when the gate voltage is 0V. In this manner, the characteristic in which the gate current flows when the gate voltage is 0 V is referred to as a normally-on characteristic. Further, a characteristic in which the gate current does not flow when the gate voltage is 0 V is referred to as a normally-off type characteristic.

Therefore, when an oxide semiconductor is used for the semiconductor film 111, it is preferable to reduce defects (typically oxygen defects) in the oxide semiconductor film as the semiconductor film 111 as much as possible. For example, it is preferable to use a spin density of g value = 1.93 measured by an electron spin resonance method in which a magnetic field is applied in a direction parallel to the surface of the film (corresponding to a defect included in the oxide semiconductor film) Density) is reduced below the lower limit of detection of the meter. By reducing the defects in the oxide semiconductor film as much as possible, it is possible to suppress the transistor 103 from being normally turned on, and to improve the electrical characteristics and reliability of the semiconductor device.

In addition to oxygen defects, hydrogen contained in an oxide semiconductor (including a hydride such as water) may also cause the threshold voltage of the transistor to fluctuate in a negative direction. A part of the hydrogen contained in the oxide semiconductor causes formation of a donor energy level to form electrons as carriers. Therefore, a transistor using an oxide semiconductor containing hydrogen easily has a normally-on characteristic.

Then, when an oxide semiconductor is used as the semiconductor film 111, it is preferable to reduce hydrogen in the oxide semiconductor film as the semiconductor film 111 as much as possible. Specifically, a semiconductor film 111 having a region in which a hydrogen concentration obtained by secondary ion mass spectrometry (SIMS: Secondary Ion Mass Spectrometry) is less than 5 × 10 ¹⁸ atoms/cm ³ , preferably 1 × 10 is formed. ¹⁸ atoms/cm ³ or less, more preferably 5 × 10 ¹⁷ atoms/cm ³ or less, further preferably 1 × 10 ¹⁶ atoms/cm ³ or less.

Further, a semiconductor film 111 having a concentration of an alkali metal or an alkaline earth metal obtained by secondary ion mass spectrometry of 1 × 10 ¹⁸ atoms / cm ³ or less, preferably 2 × 10 ¹⁶ atoms / cm ^{3 is formed.} The following areas. Sometimes, when an alkali metal and an alkaline earth metal are bonded to an oxide semiconductor, a carrier is generated to increase an off-state current of the transistor 103.

In addition, when nitrogen is contained in the oxide semiconductor film as the semiconductor film 111, electrons as carriers are generated, and the carrier density is increased to easily become an n-type. As a result, a transistor using an oxide semiconductor containing nitrogen tends to have a normally-on characteristic. Therefore, in the oxide semiconductor film, it is preferable to reduce nitrogen as much as possible. For example, it is preferable to form the semiconductor film 111 so as to have a region having a nitrogen concentration of 5 × 10 ¹⁸ atoms/cm ³ or less.

By using the oxide semiconductor film having impurities (hydrogen, nitrogen, alkali metal, alkaline earth metal, etc.) and highly purified as much as possible for the semiconductor film 111, it is possible to suppress the transistor 103 from being normally turned on. Thereby, the off-state current of the transistor 103 can be reduced to an extremely low level. Therefore, a semiconductor device having good electrical characteristics can be manufactured. In addition, it is possible to manufacture a semiconductor device with improved reliability.

Note that various experiments can be utilized to demonstrate the fact that the off-state current of the transistor using the highly purified oxide semiconductor film is low. For example, even an element having a channel width of 1 × 10 ⁶ μm and a channel length L of 10 μm can be turned off in a range of 1 V to 10 V between the source electrode and the drain electrode. The state current is below the measurement limit of the semiconductor parameter analyzer, that is, 1×10 ^-13 A or less. In this case, it is understood that the off-state current corresponding to the value of the off-state current divided by the channel width of the transistor is 100 zA/μm or less. Further, an off-state current is measured using a circuit that connects a capacitive element and a transistor and controls a charge flowing into or from the capacitive element by the transistor. At the time of this measurement, a highly purified oxide semiconductor film was used for the channel formation region of the above transistor, and the off-state current of the transistor was measured in accordance with the amount of charge per unit time of the capacitance element. As a result, it is understood that when the voltage between the source electrode and the drain electrode of the transistor is 3 V, an extremely low off-state current of several tens of yA/μm can be obtained. From this, it can be said that the off-state current of the transistor using the highly purified oxide semiconductor film is remarkably low.

In FIG. 1, the conductive film 113 is electrically connected to a pixel electrode 121 which is one electrode of a liquid crystal element formed of a light-transmitting conductive film through an opening 117.

The semiconductor film 119 formed of the light-transmitting oxide semiconductor is used as one electrode, and the light-transmitting pixel electrode 121 is used as the other electrode, and the light-transmitting insulating film contained in the transistor 103 is used (FIG. 1) The capacitor element 105 is configured as a dielectric film. That is, the capacitive element 105 has light transmissivity. Further, a semiconductor film 119 which is one electrode of the capacitor element 105 is electrically connected to the capacitor line 115.

As described above, since the capacitor element 105 has translucency, light can be transmitted through the region overlapping the liquid crystal element. Therefore, even if the capacitor element 105 is formed over a large area in the pixel 101, the high aperture ratio can be maintained, for example, 55% or more, and further 60% or more. Further, a semiconductor device in which the charge capacity in the capacitor element is increased can be obtained.

For example, in a liquid crystal display device having a high resolution, the area of the entire pixel is reduced, but the charge capacity required for the capacitive element must be secured, so that the reduction in area is limited. Therefore, in a liquid crystal display device having a high resolution, the aperture ratio becomes small. On the other hand, since the capacitive element 105 shown in the present embodiment has light transmissivity, by providing the capacitive element in the pixel, a sufficient charge capacity can be obtained in each pixel, and the aperture ratio can be improved. Typically, it is preferred to use a pixel density of 200 ppi (pixel per inch) or more, further Display device of 300 ppi or more. Further, in one aspect of the present invention, the aperture ratio can be increased, so that light of a light source such as a backlight can be efficiently utilized, whereby the power consumption of the display device can be reduced.

Next, FIG. 2 shows a cross-sectional view along the chain line A1-A2, the chain line B1-B2, and the chain line C1-C2 shown in FIG. 1; and the first drive shown in FIG. A cross-sectional view of the transistor of circuit 104. Further, a top view of the first driving circuit 104 is omitted, and a cross-sectional view of the first driving circuit 104 is shown by D1-D2 in FIG. Further, a transistor for the first driving circuit 104 can also be used for the second driving circuit 106.

First, a cross-sectional structure of the pixel 101 along the alternate long and short dash line A1-A2, the alternate long and short dash line B1-B2, and the alternate long and short dash line C1-C2 will be described.

A base insulating film 110 is provided on the substrate 102, and a semiconductor film 111 and a semiconductor film 119 are provided on the base insulating film. A signal line 109 including one of a source electrode and a gate electrode of the transistor 103 and a conductive film 113 including the other of the source electrode and the gate electrode of the transistor 103 are disposed on the semiconductor film 111, and A capacitance line 115 is provided on the semiconductor film 119. A gate insulating film 127 is provided over the semiconductor film 111, the semiconductor film 119, the signal line 109, the conductive film 113, and the capacitor line 115, and a scanning line 107 is provided on a region of the gate insulating film overlapping the semiconductor film 111. On the gate insulating film 127, the signal line 109, the semiconductor film 111, the conductive film 113, and the semiconductor film 119, an insulating film 129 serving as a protective insulating film of the transistor 103, an insulating film 131, and an insulating film 132 are provided. An opening 117 (refer to FIG. 1) reaching the conductive film 113 is provided in the insulating film 129, the insulating film 131, and the insulating film 132 to cover the opening A pixel electrode 121 (see FIG. 1) is provided in an opening manner.

One of the pair of electrodes of the capacitor element 105 shown in the present embodiment is a semiconductor film 119 formed on the base insulating film 110 in the same manner as the semiconductor film 111, and the other of the pair of electrodes is the pixel electrode 121. The dielectric between the pair of electrodes is an insulating film 129, an insulating film 131, and an insulating film 132.

A dopant may be added to the semiconductor film 119. When the semiconductor film 119 is an oxide semiconductor, for example, by adding one or more dopants selected from the group consisting of hydrogen, boron, nitrogen, fluorine, aluminum, phosphorus, arsenic, indium, tin, antimony, and rare gas elements, The oxide semiconductor layer is made n-type and the conductivity is improved. Therefore, the semiconductor film 119 can also be referred to as a conductive film, and can be used as one electrode of a capacitive element.

Further, as the semiconductor film 119 used as the conductive film, it is preferable that the hydrogen concentration is higher than the hydrogen concentration of the semiconductor film 111. In the semiconductor film 119, the hydrogen concentration obtained by secondary ion mass spectrometry (SIMS: Secondary Ion Mass Spectrometry) is 8 × 10 ¹⁹ atoms / cm ³ or more, preferably 1 × 10 ²⁰ atoms / cm ³ or more. More preferably, it is 5 × 10 ²⁰ atoms / cm ³ or more. In the semiconductor film 111, the hydrogen concentration by secondary ion mass spectrometry is 5 × 10 ¹⁹ atoms / cm ³ or less, preferably 5 × 10 ¹⁸ atoms / cm ³ or less, more preferably 1 × 10 ¹⁸ atoms. /cm ³ or less, more preferably 5 × 10 ¹⁷ atoms / cm ³ or less, further preferably 1 × 10 ¹⁶ atoms / cm ³ or less.

In addition, the resistivity of the semiconductor film 119 used as the conductive film is lower than that of the semiconductor film 111. The resistivity of the semiconductor film 119 is preferably 1 × 10 ^-8 or more and 1 × 10 ^-1 or less times the specific resistance of the semiconductor film 111, and is typically 1 × 10 ^-3 Ωcm or more and less than 1 × 10 ^{4 .} Ωcm is more preferably 1 × 10 ^-3 Ωcm or more and less than 1 × 10 ^-1 Ωcm.

In addition, the semiconductor film 119 may be formed using a material different from the semiconductor film 111 or the semiconductor film 231. That is, the semiconductor film 119 can be formed by a process different from that of the semiconductor film 111 or the semiconductor film 231.

Further, a semiconductor film is formed as in the case of forming the semiconductor film 119, and a resistive element can be formed using the semiconductor film. Moreover, the protection circuit can be constructed using the resistor element. Destruction from static electricity or the like can be reduced by providing a protection circuit.

Next, the structure of the transistor provided in the first driving circuit 104 will be described.

A conductive film 241 is provided on the substrate 102, and a base insulating film 110 is provided on the substrate and the conductive film. A semiconductor film 231 is provided on a region of the base insulating film 110 that overlaps with the conductive film 241. A wiring 229 including one of a source electrode and a drain electrode of the transistor 223 and a wiring 233 including the other of the source electrode and the drain electrode of the transistor 223 are disposed on the semiconductor film 231. A gate insulating film 127 is provided on the semiconductor film 231, the wiring 229, and the wiring 233, and a gate electrode 227 is provided in a region of the gate insulating film overlapping the semiconductor film 231. An insulating film 129 serving as a protective insulating film of the transistor 223, an insulating film 131, and an insulating film 132 are provided on the gate insulating film 127 and on the gate electrode 227. In addition, the transistor provided in the first driving circuit 104 may also adopt a structure in which the conductive film 241 is not provided.

By providing the conductive film 241 which is superposed on the gate electrode 227 via the semiconductor film 231 in the transistor 223, it is possible to reduce the gate which causes the on-state current to rise between different gate voltages. Voltage deviation. Further, the current flowing between the wiring 229 and the wiring 233 can be controlled on the surface of the semiconductor film 231 opposed to the conductive film 241, and variations in electrical characteristics between different transistors can be reduced. Further, by providing the conductive film 241, the influence of the change in the surrounding electric field on the semiconductor film 231 is alleviated, whereby the reliability of the transistor can be improved. Further, when the potential of the conductive film 241 is set to the same potential as the lowest potential of the drive circuit (Vss, for example, the potential of the wiring 229 when the potential of the wiring 229 is used as a reference), or substantially the same potential, the transistor can be reduced. The variation of the threshold voltage can thereby improve the reliability of the transistor.

Further, the insulating film provided on the gate insulating film 127, the scanning line 107, and the gate electrode 227 is not limited to the above three-layer structure, and one, two or four or more layers may be employed.

Next, the constituent elements of the above configuration will be described in detail.

Although the material of the substrate 102 or the like is not greatly limited, the substrate needs to have at least heat resistance capable of withstanding the degree of heat treatment performed in the process of the semiconductor device. For example, there may be a glass substrate, a ceramic substrate, a plastic substrate, or the like, and an alkali-free glass substrate such as barium borate glass, aluminoborosilicate glass or aluminosilicate glass may be used as the glass substrate. Further, a substrate having no light transmittance such as a stainless steel alloy can also be used. At this time, it is preferable to provide an insulating film on the surface of the substrate. In addition, as a substrate 102. A quartz substrate, a sapphire substrate, a single crystal semiconductor substrate, a polycrystalline semiconductor substrate, a compound semiconductor substrate, an SOI (Silicon On Insulator) substrate, or the like can also be used.

The base insulating film 110 may be, for example, an insulating material such as yttrium oxide, lanthanum oxynitride, lanthanum oxynitride, tantalum nitride, aluminum oxide, lanthanum oxide, gallium oxide or Ga-Zn-based metal oxide, and may have a single layer structure or a stack. The layer structure is formed. The thickness of one region of the base insulating film 110 can be set to 30 nm or more and 500 nm or less, preferably 150 nm or more and 400 nm or less.

It is preferable to use an oxide semiconductor film for the semiconductor film 111, the semiconductor film 119, and the semiconductor film 231. The oxide semiconductor film may have an amorphous structure, a single crystal structure or a polycrystalline structure. Further, the thickness of the partial region of the semiconductor film 111 is 1 nm or more and 100 nm or less, preferably 1 nm or more and 50 nm or less, more preferably 1 nm or more and 30 nm or less, and most preferably 3 nm or more and 20 nm or less.

In addition, a light shielding film may be disposed under the base insulating film 110 so as to cover the channel region of the semiconductor film 111. As the light shielding film, for example, it can be formed simultaneously with the conductive film 241.

The semiconductor which can be used for the semiconductor film 111, the semiconductor film 119, and the semiconductor film 231 has an energy gap of 2 eV or more, preferably 2.5 eV or more, more preferably 3 eV or more, and less than 3.9 eV, preferably less than 3.7. An eV, more preferably an oxide semiconductor of less than 3.5 eV. As such, by using an oxide semiconductor having a wide gap, the off-state current of the transistor 103 can be lowered. In addition, the oxide semiconductor penetrates into visible light The ratio is high, and by using it for one electrode of the capacitor element 105, a light-transmitting capacitor element can be formed, and the aperture ratio of a pixel of a liquid crystal display device or the like can be improved.

In addition, by making the oxide semiconductor film n-type, the optical band gap of the oxide semiconductor film can be set to 2.4 eV or more and 3.1 eV or less, or 2.6 eV or more and 3.0 eV or less. Further, for example, when an In-Ga-Zn-based metal oxide having an atomic ratio of In:Ga:Zn=1:1:1 is used as the oxide semiconductor film used as the semiconductor film 119, the optical band gap is 3.15eV. Further, the optical band gap of the indium tin oxide used for the pixel electrode 121 or the like is 3.7 eV to 3.9 eV. Therefore, the semiconductor film 119 can absorb light and ultraviolet light having the highest energy wavelength in the visible light transmitted through the pixel electrode 121. Since it is feared that the light containing the highest energy wavelength and the ultraviolet light may damage the eyes, the light-transmitting capacitive element 105 is used for the pixel 101, and the eye irritation can be reduced. Further, the capacitive element 105 may not overlap with the entire area of the pixel 101. By overlapping the capacitive element 105 with at least a portion of the pixel 101, it is possible to absorb light having a high energy wavelength and ultraviolet light in visible light.

The oxide semiconductor which can be used for the semiconductor film 111, the semiconductor film 119, and the semiconductor film 231 preferably contains at least indium (In) or zinc (Zn). Alternatively, it is preferred to contain both In and Zn. Further, in order to reduce variation in electrical characteristics of the transistor using the oxide semiconductor, it is preferable to have one or more stabilizers in addition to the above elements.

As a stabilizer, gallium (Ga) and tin can be mentioned. (Sn), hafnium (Hf), aluminum (Al) or zirconium (Zr). Further, examples of other stabilizers include lanthanum (La), cerium (Ce), strontium (Pr), cerium (Nd), strontium (Sm), cerium (Eu), cerium (Gd), and cerium. (Tb), Dy, Ho, Er, Tm, Yb, Lu, and the like.

As the oxide semiconductor which can be used for the semiconductor film 111, the semiconductor film 119, and the semiconductor film 231, for example, indium oxide; tin oxide; zinc oxide; an oxide containing two metals such as an In-Zn-based oxide, Sn-Zn-based oxide, Al-Zn-based oxide, Zn-Mg-based oxide, Sn-Mg-based oxide, In-Mg-based oxide, In-Ga-based oxide; oxide containing three metals, such as In-Ga-Zn-based oxide (also referred to as IGZO), In-Al-Zn-based oxide, In-Sn-Zn-based oxide, Sn-Ga-Zn-based oxide, Al-Ga-Zn-based oxide , Sn-Al-Zn-based oxide, In-Hf-Zn-based oxide, In-Zr-Zn-based oxide, In-Ti-Zn-based oxide, In-Sc-Zn-based oxide, In-Y- Zn-based oxide, In-La-Zn-based oxide, In-Ce-Zn-based oxide, In-Pr-Zn-based oxide, In-Nd-Zn-based oxide, In-Sm-Zn-based oxide, In-Eu-Zn-based oxide, In-Gd-Zn-based oxide, In-Tb-Zn-based oxide, In-Dy-Zn-based oxide, In-Ho-Zn-based oxide, In-Er-Zn Oxide-like, In-Tm-Zn-based oxide, In-Yb-Zn-based oxide, In-Lu-Zn-based oxide; oxide containing four metals, such as In-Sn-G a-Zn-based oxide, In-Hf-Ga-Zn-based oxide, In-Al-Ga-Zn-based oxide, In-Sn-Al-Zn-based oxide, In-Sn-Hf-Zn-based oxide , In-Hf-Al-Zn-based oxide.

Here, the "In-Ga-Zn-based oxide" means an oxide containing In, Ga, and Zn as main components, and the ratio of In, Ga, and Zn is not limited. Further, a metal element other than In, Ga, or Zn may be contained.

Further, as the oxide semiconductor, a material represented by InMO ₃ (ZnO) _m (m>0) can be used. Note that M represents one or more metal elements selected from Ga, Fe, Mn, and Co or an element used as the above stabilizer.

For example, In:Ga:Zn=1:1:1 (=1/3:1/3:1/3), In:Ga:Zn=2:2:1 (=2/5:2/5) can be used. : 1/5) or an In—Ga—Zn-based metal oxide having an atomic ratio of In:Ga:Zn=3:1:2 (=1/2:1/6:1/3). Alternatively, In:Sn:Zn=1:1:1 (=1/3:1/3:1/3), In:Sn:Zn=2:1:3 (=1/3:1/6) : 1/2) or an In—Sn—Zn-based metal oxide having an atomic ratio of In:Sn:Zn=2:1:5 (=1/4:1/8:5/8). Further, the atomic ratio of the metal oxide includes a variation of ±20% of the above atomic ratio as an error.

However, the material is not limited thereto, and a material having an appropriate atomic ratio can be used depending on semiconductor characteristics and electrical characteristics (field effect mobility, threshold voltage, and the like) required. Further, it is preferred to use a suitable carrier density, impurity concentration, defect density, atomic ratio of metal element and oxygen, interatomic distance, density, and the like to obtain desired semiconductor characteristics. For example, a higher field effect mobility can be obtained relatively easily when an In-Sn-Zn-based oxide is used. However, when an In-Ga-Zn-based oxide is used, the field-effect mobility can also be improved by reducing the defect density in the bulk.

In order to reduce the resistance loss, the signal line 109, the conductive film 113. The capacitor line 115 wiring 229 and the wiring 233 are preferably formed using a metal film having a low resistance. For example, a metal material such as molybdenum (Mo), titanium (Ti), tungsten (W), tantalum (Ta), aluminum (Al), copper (Cu), chromium (Cr), niobium (Nd), or strontium (Sc) may be used. Or an alloy material containing the above elements as a main component and formed in a single layer structure or a laminated structure.

As an example of the signal line 109, the conductive film 113, the capacitance line 115 wiring 229, and the wiring 233, a single layer structure using aluminum containing germanium; a two-layer structure in which titanium is laminated on aluminum; on titanium nitride a two-layer structure of stacked titanium; a two-layer structure in which tungsten is laminated on titanium nitride; a two-layer structure in which tungsten is laminated on tantalum nitride; a two-layer structure in which copper is laminated on a copper-magnesium-aluminum alloy; and nitrogen is sequentially laminated A three-layer structure of titanium, copper and tungsten.

For example, the signal line 109, the conductive film 113, the capacitor line 115 wiring 229, and the wiring 233 are preferably aluminum or copper using a low-resistance material. By using aluminum or copper, signal delay can be reduced, thereby improving display quality. In addition, since aluminum has low heat resistance, defects due to hillocks, whiskers, or migration are likely to occur. In order to prevent migration of aluminum, it is preferred to laminate a metal material having a higher melting point than aluminum such as molybdenum, titanium or tungsten on aluminum. Further, when copper is used, in order to prevent defects due to migration or diffusion of copper elements, it is preferable to laminate a metal material having a higher melting point than copper such as molybdenum, titanium or tungsten.

Further, as the material of the signal line 109, the conductive film 113, the capacitance line 115 wiring 229, and the wiring 233, a light-transmitting conductive material that can be applied to the pixel electrode 121 can be used. Further, when the semiconductor device according to one embodiment of the present invention is a reflective display device, a conductive material having no light transmittance can be used as the pixel electrode 121 or the substrate 102. material.

As the gate insulating film 127, for example, an insulating material such as hafnium oxide, hafnium oxynitride, hafnium oxynitride, tantalum nitride, aluminum oxide, hafnium oxide, gallium oxide or Ga-Zn-based metal oxide can be used, and a single layer can be used. A structure or a laminated structure is formed. In addition, in order to improve the interface characteristics between the gate insulating film 127 and the oxide semiconductor film as the semiconductor film 111, it is preferable that at least the region of the gate insulating film 127 contacting the semiconductor film 111 is formed of an insulating film containing oxygen. .

In addition, by using an insulating film having a barrier property against oxygen, hydrogen, water, or the like to the gate insulating film 127, it is possible to prevent oxygen in the oxide semiconductor film as the semiconductor film 111 from diffusing to the outside and prevent hydrogen, water, and the like from being Externally intruded into the oxide semiconductor film. Examples of the insulating film having barrier properties against oxygen, hydrogen, water, etc. include alumina, aluminum oxynitride, gallium oxide, gallium oxynitride, cerium oxide, cerium oxynitride, cerium oxide, cerium oxynitride, Niobium nitride and the like.

Further, by using a hafnium silicate (HfSiO _x) as the gate insulating film 127, hafnium silicate (HfSi _x O _y N _z) containing nitrogen, the nitrogen containing hafnium aluminate _{(HfAl x O y N z)} , oxide A high-k material such as germanium or germanium oxide can lower the gate leakage current of the transistor 103.

Further, it is preferable that the gate insulating film 127 has a structure in which a film is formed by laminating a film from the side of the gate electrode: a tantalum nitride film having a small amount of defects is provided as the first tantalum nitride film, and a second tantalum nitride film is provided as the second tantalum nitride film. A tantalum nitride film having a small amount of hydrogen detachment and a small amount of ammonia detachment is provided on the first tantalum nitride film; and the above-mentioned oxygen-containing film which can be used as the gate insulating film 127 is provided on the second tantalum nitride film. Any of the rim membranes.

As the second tantalum nitride film, it is preferred that the amount of hydrogen molecules used in the thermal desorption spectrum analysis is less than 5 × 10 ²¹ molecules/cm ³ , preferably 3 × 10 ²¹ molecules/cm ³ or less. More preferably, it is 1 × 10 ²¹ molecules/cm ³ or less, and the amount of detachment of the ammonia molecule is less than 1 × 10 ²² molecules/cm ³ , preferably 5 × 10 ²¹ molecules/cm ³ or less, more preferably 1 × 10 ²¹ molecules. A tantalum nitride film of /cm ³ or less. By using the first tantalum nitride film and the second tantalum nitride film as a part of the gate insulating film 127, as the gate insulating film 127, gate insulating having a small amount of defects and a small amount of hydrogen and ammonia removal can be formed. membrane. Thereby, the amount of hydrogen and nitrogen contained in the gate insulating film 127 diffused into the semiconductor film 111 can be reduced.

In a transistor using an oxide semiconductor, when a trap level (also referred to as an interface level) exists in an interface or a gate insulating film of an oxide semiconductor film and a gate insulating film, a threshold voltage of a transistor is easily generated. The change is typically a negative change in the threshold voltage. In addition, the trap energy level causes an increase in the sub-threshold swing (S value) which indicates the gate voltage required to change the gate current by an order of magnitude when the transistor is turned on. Further, the above electrical characteristics vary, and there is a problem that the electrical characteristics of the respective transistors vary. Therefore, by using a tantalum nitride film having a small amount of defects as the gate insulating film and providing an insulating film containing oxygen in a region in contact with the semiconductor film 111, the negative drift of the threshold voltage can be reduced, and the S value can be suppressed. Increase.

The thickness of a partial region of the gate insulating film 127 is set to 5 nm or more and 400 nm or less, preferably 10 nm or more and 300 nm or less, and more preferably 50 nm or more and 250 nm or less.

The scanning line 107, the gate electrode 227, and the conductive film 241 can be formed of a material having a single layer structure or a stacked structure, which can be applied to the signal line 109, the conductive film 113, the capacitance line 115, the wiring 229, and the wiring 233.

Further, as a material of the scanning line 107, the gate electrode 227, and a part of the conductive film 241, a metal oxide containing nitrogen, specifically, an In-Ga-Zn-based oxide containing nitrogen or In-containing nitrogen-containing oxide can be used. Sn-based oxide, nitrogen-containing In-Ga-based oxide, nitrogen-containing In-Zn-based oxide, nitrogen-containing Sn-based oxide, nitrogen-containing In-based oxide, and metal nitride film (InN, SnN, etc.) ). These materials have a work function above 5 eV (electron volts). When an oxide semiconductor is used as the semiconductor film 111 of the transistor 103, the threshold voltage of the transistor 103 can be changed in the positive direction by using a metal oxide containing nitrogen as the scanning line 107 (the gate electrode of the transistor 103). A transistor having a so-called normally closed characteristic can be realized. For example, when an In—Ga—Zn-based oxide containing nitrogen is used, an In—Ga—Zn-based oxide having a nitrogen concentration higher than that of the oxide semiconductor film of the semiconductor film 111 can be used, specifically, a nitrogen concentration of 7 atom%. The above In-Ga-Zn-based oxide.

For the insulating film 129 and the insulating film 131, for example, an oxidized insulating material such as yttrium oxide, lanthanum oxynitride, aluminum oxide, lanthanum oxide, gallium oxide or Ga-Zn-based metal oxide can be used, and it can be formed in a single layer structure or a stacked structure.

The thickness of a partial region of the insulating film 129 is set to 5 nm or more and 150 nm or less, preferably 5 nm or more and 50 nm or less, and more preferably 10 nm or more and 30 nm or less. Further, a portion of the insulating film 131 The thickness of the region is set to 30 nm or more and 500 nm or less, preferably 150 nm or more and 400 nm or less.

It is preferable that one or both of the insulating film 129 and the insulating film 131 be an oxide insulating film whose oxygen content exceeds a stoichiometric composition. Thereby, oxygen is prevented from being detached from the oxide semiconductor film, and the oxygen-permeable gate insulating film 127 contained in the oxygen-excess region is diffused to the oxide semiconductor film, whereby oxygen defects can be filled. For example, the release amount of oxygen molecules in the heat treatment at 100 ° C or higher and 700 ° C or lower, preferably 100 ° C or higher and 500 ° C or lower, measured by thermal desorption spectrum analysis (hereinafter referred to as TDS analysis) is An oxide insulating film of 1.0 × 10 ¹⁸ molecules/cm ³ or more can fill oxygen defects in the oxide semiconductor film. In addition, one or both of the insulating film 129 and the insulating film 131 may be an oxide insulating film partially having a region in which the oxygen content exceeds the stoichiometric composition (oxygen excess region), by at least overlapping the semiconductor film 111. The presence of an oxygen excess region in the region prevents oxygen from being detached from the oxide semiconductor film and allows oxygen in the oxygen excess region to diffuse into the oxide semiconductor film to fill the oxygen defect.

When the insulating film 131 is an oxidized insulating film whose oxygen content exceeds a stoichiometric composition, the insulating film 129 is preferably an oxidized insulating film that transmits oxygen. Further, in the insulating film 129, oxygen that has entered the insulating film 129 from the outside does not pass through the insulating film 129 and diffuses, and there is also oxygen remaining in the insulating film 129. Further, there is also oxygen which is included in the insulating film 129 in advance and diffused from the insulating film 129 to the outside. Therefore, the insulating film 129 is preferably an oxide insulating film having a large diffusion coefficient of oxygen.

In addition, one of the insulating film 129 and the insulating film 131 or Both of them are preferably insulating films which are resistant to nitrogen. For example, the dense oxide insulating film can be made to have a barrier property against nitrogen. Specifically, an oxide insulating film having an etching rate of 10 nm/min or less when 0.5 wt% of hydrogen fluoride is used at 25 ° C is preferably used.

In addition, when an oxide insulating film containing nitrogen such as hafnium oxynitride or hafnium oxynitride is used as one or both of the insulating film 129 and the insulating film 131, it is preferable to use SIMS (Secondary Ion Mass Spectrometry: The nitrogen concentration obtained by the sub-ion mass spectrometry is more than 3 × 10 ²⁰ atoms/cm ³ , more preferably 1 × 10 ¹⁸ atoms/cm ³ or more and 1 × 10 ²⁰ atoms/cm ^{3 , which is} lower than the detection lower limit of SIMS. The following areas are formed in a way. In this way, the amount of nitrogen moving to the semiconductor film 111 in the transistor 103 can be reduced. Further, it is thereby possible to reduce the amount of defects of the oxide insulating film itself containing nitrogen.

Further, the insulating film 132 can be formed of, for example, a nitride insulating material such as hafnium oxynitride, tantalum nitride, aluminum nitride or aluminum oxynitride, and has a single layer structure or a stacked structure.

As the insulating film 132, a nitride insulating film having a small hydrogen content may be provided. As the nitride insulating film, for example, a release of hydrogen molecules measured by a TDS analysis performed in a heat treatment at a surface temperature of the film of 100 ° C or more and 700 ° C or less, preferably 100 ° C or more and 500 ° C or less can be used. The amount is less than 5.0 × 10 ²¹ molecules/cm ³ , preferably less than 3.0 × 10 ²¹ molecules/cm ³ , more preferably less than 1.0 × 10 ²¹ molecules/cm ³ of the nitrided insulating film.

The thickness of a partial region of the insulating film 132 is set to a thickness capable of suppressing entry of impurities such as hydrogen or water from the outside. For example, set it It is set to 50 nm or more and 200 nm or less, preferably 50 nm or more and 150 nm or less, and more preferably 50 nm or more and 100 nm or less. By providing the insulating film 132, impurities such as carbon are blocked by the insulating film 132, and impurities are prevented from moving from the outside to the semiconductor film 111 of the transistor 103 and the semiconductor film 231 of the transistor 223, whereby variation in electrical characteristics of the transistor can be reduced.

Note that when the insulating film provided on the gate insulating film 127, the scanning line 107, and the gate electrode 227 is one layer, the insulating film 131 is preferably provided. Further, when the insulating film has two layers, it is preferable to provide the insulating film 131 and the insulating film 132 from the side of the semiconductor film.

Further, the insulating film formed between the gate insulating film 127, the scanning line 107 and the gate electrode 227, the pixel electrode 121, the conductive film 241, and the wiring which can be simultaneously formed may include CVD by using an organic decane gas. An oxidized insulating film formed by a method (chemical vapor deposition method) is typically a ruthenium oxide film.

The thickness of the hafnium oxide film may be 300 nm or more and 600 nm or less. As the organic decane gas, ethyl ortho-nonanoate (TEOS: chemical formula: Si(OC ₂ H ₅ ) ₄ ), tetramethyl decane (TMS: chemical formula: Si(CH ₃ ) ₄ ), tetramethylcyclotetrafluorene can be used. Oxytomane (TMCTS), octamethylcyclotetraoxane (OMCTS), hexamethyldioxane (HMDS), triethoxydecane (SiH(OC ₂ H ₅ ) ₃ ), tris (dimethylamine) a compound containing ruthenium such as decane (SiH(N(CH ₃ ) ₂ ) ₃ ).

By forming the yttrium oxide film by a CVD method using an organic decane gas, the flatness of the surface of the element portion formed on the substrate 102 can be improved. As a result, even if a planarizing film formed of an organic resin is not provided, It can also reduce the alignment disorder of the liquid crystal, can reduce light leakage, and can improve the contrast. Of course, an organic resin may be used instead of the hafnium oxide film, and a laminate including the hafnium oxide film and an organic resin may also be used.

As the pixel electrode 121, indium tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium zinc oxide, addition may be used. It is formed of a light-transmitting conductive material such as indium tin oxide which is yttria.

Next, each component included in the pixel 101 shown in the present embodiment will be described.

FIG. 4A shows an example of a circuit diagram of the above-described pixel 101. The pixel 101 includes a transistor 103, a capacitive element 105, and a liquid crystal element 108. The gate electrode of the transistor 103 is electrically connected to the scan line 107, one of the source electrode and the drain electrode is electrically connected to the signal line 109, and the other of the source electrode and the drain electrode is electrically connected to one of the capacitor elements 105. The electrode and one electrode (pixel electrode) of the liquid crystal element 108. Further, the other electrode of the capacitive element 105 is electrically connected to the capacitance line 115, and the other electrode (counter electrode) of the liquid crystal element 108 is electrically connected to a wiring that supplies a counter potential to the counter electrode.

The liquid crystal element 108 controls the transmission or non-transmission of light by the optical modulation action of the liquid crystal sandwiched between the substrate on which the transistor 103 and the pixel electrode are formed and the opposite substrate (for example, the substrate on which the counter electrode is formed). Further, the optical modulation of the liquid crystal is controlled by an electric field (including a longitudinal electric field or an oblique electric field) applied to the liquid crystal. Also, when on the same substrate When a pixel electrode and a counter electrode (also referred to as a common electrode) are formed, an electric field applied to the liquid crystal becomes a transverse electric field.

In addition, FIG. 4B shows an example of a detailed circuit diagram of the pixel 101. As shown in FIG. 4B and FIG. 2, the transistor 103 includes: a scan line 107 including a gate electrode; a signal line 109 including one of a source electrode and a drain electrode; and a source electrode and a drain electrode The other conductive film 113.

In the capacitive element 105, the semiconductor film 119 connected to the capacitance line 115 is used as one electrode. Further, the pixel electrode 121 connected to the conductive film 113 including the other of the source electrode and the drain electrode is used as the other electrode. In addition, the insulating film 129, the insulating film 131, and the insulating film 132 provided between the semiconductor film 119 and the pixel electrode 121 are used as a dielectric film.

The liquid crystal element 108 includes a pixel electrode 121, a counter electrode 154, and a liquid crystal layer disposed between the pixel electrode 121 and the counter electrode 154.

In the capacitor element 105, even if the semiconductor film 119 is high in resistance like the semiconductor film 111, the semiconductor film 119 is used as an electrode of the capacitor element 105. This is because the pixel electrode 121 can be used as a gate electrode, and the insulating film 129, the insulating film 131, and the insulating film 132 can be used as a gate insulating film, and the capacitor line 115 can be used as a source electrode or a drain electrode. As a result, the capacitor element 105 can be operated in the same manner as the transistor, and the semiconductor film 119 can be turned on. Therefore, the semiconductor film 119 can be used as one electrode of the capacitive element 105.

Next, a method of manufacturing the semiconductor device shown in FIGS. 1 and 2 will be described with reference to FIGS. 5A and 5B, and FIGS. 6A and 6B.

First, a conductive film 241 is formed on the substrate 102, and the base insulating film 110 is formed to cover the conductive film.

The conductive film can be formed by forming a conductive film using the above material, forming a mask on the conductive film, and performing processing using the mask. The conductive film can be formed by various film forming methods such as a vapor deposition method, a CVD method, a sputtering method, or a spin coating method. Note that the thickness of the conductive film is not particularly limited, and the thickness may be determined in consideration of the formation of the required time, the desired resistivity, and the like. The mask may be, for example, a photoresist mask formed by a photolithography process. In addition, the conductive film may be processed by one or both of dry etching and wet etching.

The base insulating film 110 can be formed using the above materials. The base insulating film can be formed by various film forming methods such as a vapor deposition method, a CVD method, a sputtering method, and a spin coating method.

Next, the semiconductor film 111, the semiconductor film 119, and the semiconductor film 231 are formed (see FIG. 1). An oxide semiconductor film can be formed using the above oxide semiconductor, and a mask can be formed on the oxide semiconductor film, and the semiconductor film 111, the semiconductor film 119, and the semiconductor film 231 can be formed by processing with the mask. The oxide semiconductor film can be formed by a sputtering method, a coating method, a pulsed laser deposition method, a laser ablation method, or the like. The semiconductor film 111 and the semiconductor film 119 from which the elements are separated can be directly formed on the base insulating film 110 by using a printing method. When the oxide semiconductor film is formed by a sputtering method, it can be suitably used as a power source device for generating plasma Use an RF power supply unit, an AC power supply unit, or a DC power supply unit. As the sputtering gas, a mixed gas of a rare gas (typically argon), an oxygen gas, a rare gas, and oxygen can be suitably used. Further, when a mixed gas of a rare gas and oxygen is used, it is preferred to increase the proportion of oxygen relative to the oxygen of the rare gas. Further, the target may be appropriately selected depending on the composition of the oxide semiconductor film to be formed. In addition, the mask may be, for example, a photoresist mask formed by a photolithography process. Further, the processing of the oxide semiconductor film can be performed using one or both of dry etching and wet etching. The etching conditions (etching gas, etchant, etching time, temperature, etc.) are appropriately set depending on the material so as to be etched into a desired shape.

Further, the above oxide semiconductor film can also be formed by a CVD method. As the CVD method, a thermal CVD method such as a MOCVD (Metal Organic Chemical Vapor Deposition) method or an ALD (Atomic Layer Deposition) method can be used.

The thermal CVD method is a film forming method that does not use plasma, and therefore has an advantage that no defects due to plasma damage are generated.

Film formation by a thermal CVD method can be carried out by simultaneously supplying a source gas and an oxidant into a processing chamber, and setting the pressure in the processing chamber to atmospheric pressure or reduced pressure to cause a reaction in the vicinity of the substrate or on the substrate.

Further, film formation by the ALD method can be carried out by setting the pressure in the treatment chamber to atmospheric pressure or reduced pressure, sequentially introducing the source gas for the reaction into the treatment chamber, and repeatedly introducing the gas in this order. body. For example, two or more source gases are sequentially supplied into the processing chamber by switching each of the switching valves (also referred to as high speed valves). In order to prevent mixing of a plurality of source gases, for example, an inert gas (argon or nitrogen, etc.) or the like is introduced at the same time as or after the introduction of the first source gas, and then the second source gas is introduced. Note that when the first source gas and the inert gas are simultaneously introduced, the inert gas is used as the carrier gas, and in addition, the inert gas may be introduced while introducing the second source gas. Alternatively, the first source gas may be discharged by vacuum pumping instead of introducing the inert gas, and then the second source gas may be introduced. The first source gas is attached to the surface of the substrate to form a first layer, and the second source gas introduced thereafter reacts with the first layer, whereby the second layer is laminated on the first layer to form a thin film. By introducing the gas a plurality of times in this order repeatedly until a desired thickness is obtained, a film having a good step coverage can be formed. Since the thickness of the film can be adjusted according to the number of times the gas is repeatedly introduced in order, the ALD method can accurately adjust the thickness and is suitable for forming a micro-crystal.

For example, when an In-Ga-Zn-O film is formed, trimethylindium, trimethylgallium, and dimethylzinc are used. Further, the chemical formula of trimethylindium is In(CH ₃ ) ₃ . In addition, the chemical formula of trimethylgallium is Ga(CH ₃ ) ₃ . Further, the chemical formula of dimethyl zinc is Zn(CH ₃ ) ₂ . Further, not limited to the above combination, triethylgallium (chemical formula Ga(C ₂ H ₅ ) ₃ ) may be used instead of trimethylgallium, and diethylzinc (chemical formula Zn(C ₂ H ₅ ) ₂ ) may be used. ) instead of dimethyl zinc.

For example, when an In-Ga-Zn-O film is formed by an ALD method, In(CH ₃ ) ₃ gas and O ₃ gas are sequentially introduced repeatedly to form an InO ₂ layer, and then Ga(CH ₃ ) ₃ gas and O ₃ gas are simultaneously introduced. A GaO layer is formed, and then a ZnO layer is formed by simultaneously introducing a Zn(CH ₃ ) ₂ gas and an O ₃ gas. Note that the order of these layers is not limited to the above examples. Further, these gases may be mixed to form a mixed compound layer such as an In-Ga-O layer, an In-Zn-O layer, a Ga-In-O layer, a Zn-In-O layer, a Ga-Zn-O layer, or the like. Note that although H ₂ O gas obtained by bubbling with an inert gas such as Ar may be used instead of O ₃ gas, it is preferable to use O ₃ gas not containing H. Alternatively, In(C ₂ H ₅ ) ₃ gas may be used instead of In(CH ₃ ) ₃ gas. Further, a Ga(C ₂ H ₅ ) ₃ gas may be used instead of the Ga(CH ₃ ) ₃ gas. It is also possible to use In(C ₂ H ₅ ) ₃ gas instead of In(CH ₃ ) ₃ gas. Further, Zn(CH ₃ ) ₂ gas can also be used.

After the semiconductor film 111, the semiconductor film 119, and the semiconductor film 231 are formed, heat treatment is preferably performed to dehydrogenate or dehydrate the oxide semiconductor film as the semiconductor film 111, the semiconductor film 119, and the semiconductor film 231. The temperature of the heat treatment is typically 150 ° C or higher and lower than the strain point of the substrate, preferably 200 ° C or higher and 450 ° C or lower, more preferably 300 ° C or higher and 450 ° C or lower. Further, the heat treatment may be performed on the oxide semiconductor film before being processed into the semiconductor film 111, the semiconductor film 119, and the semiconductor film 231.

In the heat treatment, the heat treatment device is not limited to the electric furnace, and a device that heats the object to be treated by heat conduction or heat radiation such as a medium from a heated gas may be used. For example, an RTA (Rapid Thermal Anneal) device such as a GRTA (Gas Rapid Thermal Anneal) device or an LRTA (Lamp Rapid Thermal Anneal) device can be used. The LRTA device is a device that heats an object to be treated by radiation (electromagnetic wave) emitted from a lamp such as a halogen lamp, a metal halide lamp, a xenon arc lamp, a carbon arc lamp, a high pressure sodium lamp, or a high pressure mercury lamp. The GRTA device is a device that performs heat treatment using a high-temperature gas.

This heat treatment can be carried out in an atmosphere of nitrogen, oxygen, ultra-dry air (water having a water content of 20 ppm or less, preferably 1 ppm or less, more preferably 10 ppb or less) or a rare gas (argon, helium or the like). Further, it is preferable that hydrogen, water, or the like is not contained in the nitrogen, oxygen, ultra-dry air or rare gas. It is also possible to carry out heating in an oxygen atmosphere after heating in an inert gas atmosphere. Further, it is preferred to set the processing time to 3 minutes to 24 hours.

Here, a dopant may be added to the semiconductor film 119. A method of adding a dopant to the semiconductor film 119 is as follows: a mask is provided in a region other than the semiconductor film 119, and a mask selected from the group consisting of hydrogen, boron, and nitrogen is added by ion implantation or ion doping or the like. One or more dopants of fluorine, aluminum, phosphorus, arsenic, indium, tin, antimony, and rare gas elements. Further, the semiconductor film 119 may be exposed to a plasma containing the dopant to add the dopant instead of the ion implantation method or the ion doping method. Further, heat treatment may be performed after the addition of the dopant. This heat treatment can be appropriately performed with reference to the details of the heat treatment for dehydrogenating or dehydrating the semiconductor film 111 and the semiconductor film 119.

Next, the signal line 109, the conductive film 113, the capacitance line 115, the wiring 229, and the wiring 233 are formed. A conductive film can be formed by using the above material, and a mask is formed on the conductive film, and the mask is used for adding The signal line 109, the conductive film 113, the capacitance line 115, the wiring 229, and the wiring 233 are formed. The formation of the mask and the processing can be performed in the same manner as the conductive film 241.

Next, the gate insulating film 127 is formed to cover the base insulating film 110, the semiconductor film 111, the semiconductor film 119, the semiconductor film 231, the signal line 109, the conductive film 113, the capacitor line 115, the wiring 229, and the wiring 233.

The gate insulating film 127 can be formed by various film forming methods such as a CVD method or a sputtering method using the above materials. Further, when gallium oxide is used as the gate insulating film 127, it can be formed by a MOCVD (Metal Organic Chemical Vapor Deposition) method.

Next, a scanning line 107 is formed in a region overlapping the semiconductor film 111 on the gate insulating film 127, and a gate electrode 227 is formed in a region overlapping the semiconductor film 231 (see FIG. 5B).

A conductive film is formed by using the above material, and a mask is formed on the conductive film, and the scanning line 107 and the gate electrode 227 can be formed by processing with the mask. The formation of the mask and the processing can be performed in the same manner as the conductive film 241.

Next, an insulating film 129, an insulating film 131, and an insulating film 132 are formed over the gate insulating film 127, the scanning line 107, and the gate electrode 227 (see FIG. 6A). Further, it is preferable to continuously form the insulating film 129, the insulating film 131, and the insulating film 132. By continuously forming the above-described insulating film, it is possible to suppress impurities from being mixed into the insulating film 129, the insulating film 131, and the insulating film 132. Each interface.

The insulating film 129, the insulating film 131, and the insulating film 132 can be formed by various film forming methods such as a CVD method or a sputtering method using the above materials.

For example, the insulating film 129 can be formed using the above-described oxide insulating film. Note that a case where a hafnium oxide film or a hafnium oxynitride film is formed as the oxide insulating film will be described here. The formation condition is such that the temperature of the substrate provided in the vacuum venting processing chamber of the plasma CVD apparatus is maintained at 180° C. or higher and 400° C. or lower, preferably 200° C. or higher and 370° C. or lower, and introduced into the processing chamber. The deposition gas and the oxidizing gas containing ruthenium in the source gas are set to a pressure in the treatment chamber of 20 Pa or more and 250 Pa or less, preferably 40 Pa or more and 200 Pa or less, to supply high-frequency electric power to the electrodes provided in the processing chamber.

Typical examples of the deposition gas containing ruthenium include decane, acetane, propane, fluorinated decane, and the like. Examples of the oxidizing gas include oxygen, ozone, nitrous oxide, and nitrogen dioxide.

Further, by making the amount of the oxidizing gas 100 times or more of the deposition gas containing cerium, the dangling bonds in the insulating film 129 can be reduced while reducing the hydrogen content in the insulating film 129. Oxygen diffused from the insulating film 131 is sometimes trapped by the dangling bonds in the insulating film 129, so that when the dangling bonds in the insulating film 129 are reduced, oxygen in the insulating film 131 can be efficiently diffused to the semiconductor film through the gate insulating film 127. In the 111 and the semiconductor film 231, oxygen defects in the oxide semiconductor film as the semiconductor film 111 and the semiconductor film 231 can be filled. As a result, it is possible to reduce the incorporation of the oxide semiconducting The hydrogen content in the body film can also reduce oxygen defects in the oxide semiconductor film.

When the above-described oxide insulating film including the oxygen excess region or an oxide insulating film having an oxygen content exceeding a stoichiometric composition is used as the insulating film 131, the insulating film 131 can be formed under the following formation conditions. Note that a case where a hafnium oxide film or a hafnium oxynitride film is formed as the oxide insulating film will be described here. The formation condition is an example in which the temperature of the substrate in the vacuum evacuation processing chamber provided in the plasma CVD apparatus is maintained at 180° C. or higher and 260° C. or lower, preferably 180° C. or higher and 230° C. Hereinafter, the source gas is introduced into the processing chamber, and the pressure in the processing chamber is 100 Pa or more and 250 Pa or less, preferably 100 Pa or more and 200 Pa or less, and 0.17 W/cm ² or more and 0.5 W/cm are supplied to the electrodes provided in the processing chamber. ² or less, preferably ² or less of the high frequency power 0.25W / cm ² and not more than 0.35W / cm.

As the source gas of the insulating film 131, a source gas that can be applied to the insulating film 129 can be used.

As a condition for forming the insulating film 131, by supplying the high-frequency power of the above-described power density in the processing chamber of the above-described pressure, the decomposition efficiency of the source gas is improved in the plasma, the oxygen radical is increased, and the oxidation of the source gas is promoted. Therefore, the oxygen content in the insulating film 131 is larger than the stoichiometric composition. However, in the case where the substrate temperature is the temperature at which the above-described forming conditions are performed, since the bonding force between cerium and oxygen is low, a part of oxygen is detached by heating. Thereby, an oxide insulating film whose oxygen content exceeds the stoichiometric composition and a part of oxygen is removed by heating can be formed.

In addition, by forming the thickness of the insulating film 131 Since it is thick, the amount of oxygen which is detached by heating can be increased. Therefore, it is preferable to form the insulating film 131 as a film thicker than the insulating film 129. By providing the insulating film 129, good coverage can be achieved even if the insulating film 131 is formed thick.

When a nitride insulating film having a small hydrogen content is formed as the insulating film 132, the insulating film 132 can be formed using the following conditions. Note that a case where a tantalum nitride film is formed as the nitride insulating film will be described here. The formation condition is an example in which the temperature of the substrate in the vacuum evacuation processing chamber provided in the plasma CVD apparatus is maintained at 80° C. or higher and 400° C. or lower, preferably 200° C. or higher and 370° C. Hereinafter, the source gas is introduced into the processing chamber, and the pressure in the processing chamber is set to 100 Pa or more and 250 Pa or less, preferably 100 Pa or more and 200 Pa or less, and high frequency electric power is supplied to the electrodes provided in the processing chamber.

As the source gas of the insulating film 132, a deposition gas containing ruthenium, nitrogen, and ammonia is preferably used. Typical examples of the deposition gas containing ruthenium include decane, acetane, propane, fluorinated decane, and the like. Further, it is preferable that the flow rate of nitrogen is 5 times or more and 50 times or less, more preferably 10 times or more and 50 times or less, of the flow rate of ammonia. By using ammonia as a source gas, decomposition of a deposition gas containing cerium and nitrogen can be promoted. This is because the ammonia is dissociated by the plasma energy or the thermal energy, and the energy generated during the dissociation contributes to the bonding of the deposition gas molecules containing cerium and the decomposition of the bonding of the nitrogen molecules. Thereby, it is possible to form a tantalum nitride film which has a small hydrogen content and can suppress entry of impurities such as hydrogen or water from the outside.

Preferably, it is performed after at least the insulating film 131 is formed. In the heat treatment, excess oxygen contained in the insulating film 129 or the insulating film 131 is diffused into the semiconductor film 111 and the semiconductor film 231 through the gate insulating film 127, thereby filling the oxide semiconductor film as the semiconductor film 111 and the semiconductor film 231. Oxygen deficiency. This heat treatment can be appropriately performed with reference to the details of the heat treatment for dehydrogenating or dehydrating the semiconductor film 111 and the semiconductor film 231.

Next, an opening 117 reaching the conductive film 113 is formed in a region where the insulating film 129, the insulating film 131, and the insulating film 132 overlap the conductive film 113 (see FIG. 1).

Next, by forming the pixel electrode 121, the semiconductor device shown in FIGS. 1 and 2 can be manufactured (see FIG. 6B). The pixel electrode 121 can be formed by forming a conductive film that is in contact with the conductive film 113 through the opening 117 using the above-exemplified materials, forming a mask on the conductive film, and forming it by using the mask. Further, the formation of the mask and the processing can be performed in the same manner as the conductive film 241.

Further, in the semiconductor device of one embodiment of the present invention, the structure of the capacitor element can be appropriately changed. For example, as shown in the cross-sectional view of the capacitive element 105 in FIG. 7A, the gate insulating film 127 may also be removed from the dielectric portion of the capacitive element 105. Thereby, the film thickness of the dielectric portion can be made thin, thereby increasing the charge capacity of the capacitor element 105. Further, the gate insulating film 127 can be partially removed by forming a mask on the gate insulating film and performing processing using the mask. Further, the formation of the mask and the processing can be performed in the same manner as the conductive film 241. In addition, when the gate electrode 227 is formed using a halftone mask, the gate insulating film can be removed. Part of 127. At this time, the photolithography process can be reduced. Further, a structure in which one of the insulating film 129 and the insulating film 131 is removed may also be employed.

Further, as shown in the cross-sectional view of the capacitor element 105 in FIG. 7B, the gate insulating film 127, the insulating film 129, and the insulating film 131 may be removed from the dielectric portion of the capacitor element 105. Thereby, the film thickness of the dielectric portion can be made thinner, thereby increasing the charge capacity of the capacitor element 105.

Further, in the capacitor element 105 shown in FIG. 7B, a structure in which the semiconductor film 119 is in contact with the insulating film 132 is employed. As described above, the insulating film 132 is preferably a nitride insulating film. The nitride insulating film contains a large amount of nitrogen and hydrogen, and these nitrogen and hydrogen can be diffused to the semiconductor film 119. When an oxide semiconductor is used as the semiconductor film 119, a part of nitrogen and hydrogen which enter the oxide semiconductor contributes to formation of a donor energy level at which a carrier is generated, so that the oxide semiconductor layer can be made n-type. Therefore, the conductivity of the semiconductor film 119 can be increased, and the process of doping the semiconductor film 119 with impurities can be omitted.

Further, as shown in FIG. 8, a structure in which a nitride insulating film 118 is provided between the semiconductor film 119 which is one electrode of the capacitor element 105 and the base insulating film 110 may be employed. By adopting such a configuration, nitrogen and hydrogen can be diffused from the nitride insulating film 118 to the semiconductor film 119 in the same manner as in FIG. 7B, whereby the conductivity of the semiconductor film 119 can be improved. Further, a nitride insulating film 118 can be formed by forming a film which can be used for the insulating film 132, forming a mask on the film, and performing processing using the mask. Further, the formation of the mask and the processing can be performed in the same manner as the conductive film 241. In addition, also The structure of the capacitive element shown in Fig. 7A or Fig. 7B can be combined in the capacitive element.

Further, in the semiconductor device according to the aspect of the invention, the shape of the transistor provided in the pixel is not limited to the shape of the transistor shown in FIGS. 1 and 2, and can be appropriately changed. For example, the transistor may have a shape in which one of the source electrode and the germanium electrode included in the signal line 109 is U-shaped (C-shaped, Japanese katakana). "shape or horseshoe type", and surrounds the shape of the conductive film including the other of the source electrode and the germanium electrode. By adopting the above shape, even if the area of the transistor is small, a sufficient channel width can be secured, thereby It is possible to increase the amount of the drain current (also referred to as the on-state current) flowing when the transistor is turned on.

Further, in the pixel 101 described above, although a transistor having one gate electrode is shown as a transistor, a transistor having two gate electrodes opposed to each other across the semiconductor film 111 may be used. Further, as a structure of a transistor having two gate electrodes, for example, a transistor having a gate electrode 227 and a conductive film 241 for the first driving circuit 104 shown in FIG. 2 can be referred to.

The transistor having the two gate electrodes described above has a conductive film under the base insulating film 110 of the transistor 103 described in the present embodiment. The conductive film overlaps at least the channel formation region of the semiconductor film 111. By disposing the conductive film at a position overlapping the channel formation region of the semiconductor film 111, it is preferable to set the potential of the conductive film to the lowest potential of the video signal input to the signal line 109. Thereby, the current flowing between the source electrode and the drain electrode can be controlled on the surface of the semiconductor film 111 opposed to the conductive film, To reduce the deviation of the electrical characteristics of the transistor. Further, by providing the conductive film, the influence of the change in the surrounding electric field on the semiconductor film 111 can be alleviated, and the reliability of the transistor can be improved.

The conductive film can be formed using the same material and method as the conductive film 241, the scanning line 107, the signal line 109, the pixel electrode 121, and the like.

As described above, as one electrode of the capacitor element, by using a semiconductor film formed in the same forming process as the semiconductor film included in the transistor, it is possible to manufacture a capacitor having an increased aperture ratio while increasing the charge capacity. A semiconductor device of a component. Thereby, a semiconductor device excellent in display quality can be obtained.

A semiconductor film simultaneously formed in a process of forming a semiconductor film included in a transistor is used as one electrode of a capacitor element, whereby an aperture ratio can be manufactured without increasing the number of masks required for the photolithography process A semiconductor device having a high capacitance element having a large charge capacity.

In addition, since the oxygen defect of the oxide semiconductor film of the semiconductor film included in the transistor is reduced and impurities such as hydrogen are reduced, the semiconductor device of one embodiment of the present invention becomes a semiconductor device having excellent electrical characteristics.

This embodiment can be combined as appropriate with other embodiments shown in the present specification.

Embodiment 2

In the present embodiment, the description described in the above embodiment will be described. Among the transistors and capacitor elements in the semiconductor device, one can be used as an oxide semiconductor film of a semiconductor film.

The oxide semiconductor can be in a non-single crystal state. The non-single crystal includes, for example, CAAC (C Axis Aligned Crystal), polycrystalline, microcrystalline, or amorphous.

The oxide semiconductor may also have CAAC. Note that an oxide semiconductor including CAAC is referred to as CAAC-OS (c-axis aligned crystalline oxide semiconductor).

In some cases, the crystal portion can be confirmed when the CAAC-OS is observed using a transmission electron microscope (TEM: Transmission Electron Microscope). Further, in many cases, in the observation image of the TEM, the size of the crystal portion included in the CAAC-OS is a size that can be accommodated in a cube having a side length of 100 nm. Further, when CAAC-OS is observed by TEM, the boundary between the crystal portion and the crystal portion may not be clearly confirmed. Further, when CAAC-OS is observed by TEM, the grain boundary may not be clearly confirmed. CAAC-OS does not have a clear grain boundary, so segregation of impurities is not easily generated. In addition, CAAC-OS does not have a clear grain boundary, so the density of defect states is rarely high. In addition, CAAC-OS does not have a clear grain boundary, so the electron mobility is low.

The CAAC-OS has a plurality of crystal portions, and in some cases, the c-axis coincides in a direction parallel to a normal vector of a surface on which the CAAC-OS is formed or a normal vector of a surface of the CAAC-OS. Therefore, an X-ray diffraction (XRD: X-Ray Diffraction) device was used, and the CAAC-OS was analyzed by the Out-of-plane method, and a peak was sometimes observed in the vicinity of 2θ of 31°. In the crystal of InGaZnO ₄ , a peak near 2θ of 31° indicates that it is aligned to the (009) plane. In addition, CAAC-OS peaks around 2θ at 36°. In the crystal of ZnGa ₂ O ₄ , a peak near 2θ of 36° indicates that it is aligned to the (222) plane. Preferably, in CAAC-OS, a peak occurs when 2θ is around 31° and a peak does not occur when 2θ is around 36°.

Further, CAAC-OS may have different directions of the a-axis and the b-axis between different crystal parts. In the CAAC-OS having crystals of InGaZnO ₄ , an XRD apparatus was used and analyzed by an in-plane method in which X-rays were incident from a direction perpendicular to the c-axis, and 2θ was observed to be a peak near 56°. The peak around 2θ of 56° represents the (110) plane of the crystal of InGaZnO ₄ . Here, when the sample is rotated and the sample is rotated (Φ scan) with the 2θ being fixed at around 56° and the normal vector of the surface as the axis (Φ axis), the directions of the a-axis and the b-axis are uniform. Six symmetry peaks appear in the single crystal oxide semiconductor, while no significant peaks appear in the CAAC-OS.

As described above, in the CAAC-OS, the c-axis is sometimes aligned and the a-axis or/and the b-axis are not substantially macroscopically inconsistent.

In addition, spots (bright spots) are sometimes observed in the electronic diffraction pattern of CAAC-OS. Note that an electron diffraction pattern obtained by using an electron beam having an electron beam diameter of 10 nm Φ or less or 5 nm Φ or less is particularly referred to as a nanobeam electron diffraction pattern.

Figure 10A is a nanobeam of a sample including CAAC-OS Sub-diffraction pattern. Here, the sample was cut along a direction perpendicular to the surface on which the CAAC-OS was formed, and sliced to have a thickness of about 40 nm. Further, an electron beam having an electron beam diameter of 1 nm Φ is incident here from a direction perpendicular to the cross section of the sample. As can be seen from Fig. 10A, spots can be observed in the nanobeam electron diffraction pattern of CAAC-OS.

In the crystal portion included in the CAAC-OS, the c-axis coincides in the direction parallel to the normal vector of the surface on which the CAAC-OS is formed or the normal vector of the surface of the CAAC-OS. Further, the metal atoms are arranged in a triangular or hexagonal shape when viewed from a direction perpendicular to the ab plane, and when viewed from a direction perpendicular to the c-axis, the metal atoms are arranged in a layer shape or the metal atoms and the oxygen atoms are arranged in a layer shape. In addition, the directions of the a-axis and the b-axis may be different between different crystal parts. In the present specification, the term "vertical" includes a range of 80° to 100°, preferably a range of 85° to 95°. Also, the term "parallel" includes a range of -10 to 10, preferably a range of -5 to 5 .

Since the c-axis of the crystal portion included in the CAAC-OS is uniform in the direction parallel to the normal vector of the surface on which the CAAC-OS is formed or the normal vector of the surface of the CAAC-OS, sometimes according to CAAC-OS The shape (the cross-sectional shape of the surface on which the CAAC-OS is formed or the cross-sectional shape of the surface of the CAAC-OS) may be different from each other in the direction of the c-axis. Further, the crystal portion is formed by a crystallization treatment such as heat treatment at the time of film formation or after film formation. Therefore, the c-axis of the crystal portion coincides in the direction parallel to the normal vector of the surface on which the CAAC-OS is formed or the normal vector of the surface of the CAAC-OS.

CAAC-OS can sometimes be formed by reducing the concentration of impurities. Here, the impurity means an element other than the main component of an oxide semiconductor such as hydrogen, carbon, ruthenium or a transition metal element. In particular, the bonding force of an element such as cerium with oxygen is stronger than the bonding force of a metal element constituting the oxide semiconductor with oxygen. Therefore, when the element extracts oxygen from the oxide semiconductor, the atomic arrangement of the oxide semiconductor is sometimes disturbed, and the crystallinity is lowered. In addition, since the atomic radius (or molecular radius) of heavy metals such as iron or nickel, argon, carbon dioxide, and the like is large, the atomic arrangement of the oxide semiconductor may be disturbed, and the crystallinity of the oxide semiconductor may be lowered. Therefore, CAAC-OS is an oxide semiconductor having a low impurity concentration. Further, impurities contained in the oxide semiconductor sometimes become a source of carrier generation.

Further, in CAAC-OS, the distribution of the crystal parts may be uneven. For example, in the case of forming a CAAC-OS, when crystal growth is performed from the surface side of the oxide semiconductor, the proportion of the crystal portion in the vicinity of the surface of the oxide semiconductor may be higher than that in which the oxide semiconductor is formed. The proportion of the crystal portion near the surface. Further, when impurities are mixed into the CAAC-OS, the crystallinity of the crystal portion in the impurity-incorporated region may be lowered.

In addition, CAAC-OS can be formed by reducing the density of defect states. In an oxide semiconductor, an oxygen defect is a defect level. Oxygen defects sometimes become trap energies or become sources of carrier generation by trapping hydrogen. In order to form CAAC-OS, it is important not to generate oxygen defects in the oxide semiconductor. Therefore, CAAC-OS is an oxide semiconductor having a low defect state density. Alternatively, CAAC-OS is an oxide semiconductor having less oxygen deficiency.

A state in which the impurity concentration is low and the defect state density is low (the number of oxygen defects is small) is referred to as "high purity essence" or "substantially high purity essence". An oxide semiconductor having a high-purity essence or a substantially high-purity essence has a small carrier generation source, and thus its carrier density can sometimes be lowered. Therefore, a transistor in which the oxide semiconductor is sometimes used in the channel formation region rarely has a negative threshold voltage (also referred to as a normally-on characteristic). Further, an oxide semiconductor having a high-purity essence or a substantially high-purity essence has a low density of defect states, and thus its trap state density is sometimes lowered. Therefore, the change in electrical characteristics of the transistor in which the oxide semiconductor is used in the channel formation region is small, and the transistor is highly reliable. Further, the charge trapped by the trap level of the oxide semiconductor takes a long time until it is released, and sometimes acts like a fixed charge. Therefore, the electrical characteristics of the transistor in which the oxide semiconductor having a high trap state density is used for the channel formation region are sometimes unstable.

Further, in a transistor using CAAC-OS having a high-purity essence or a substantially high-purity essence, fluctuations in electrical characteristics due to irradiation with visible light or ultraviolet light are small.

The CAAC-OS can be formed, for example, by a sputtering method using a DC power source.

The oxide semiconductor can be in a polycrystalline state. Note that an oxide semiconductor including polycrystalline is referred to as a polycrystalline oxide semiconductor. The polycrystalline oxide semiconductor includes a plurality of crystal grains.

In the image of the polycrystalline oxide semiconductor observed by TEM, crystal grains may be observed. The crystal grains included in the polycrystalline oxide semiconductor are in the observation image using TEM, and in most cases, the particle size is 2 nm or more and 300 nm or less, 3 nm or more and 100 nm or less, or 5 nm or more and 50 nm or less. Further, in the image of the polycrystalline oxide semiconductor observed by TEM, the boundary between the crystal grains and the crystal grains may be confirmed. Further, for example, in a video of a polycrystalline oxide semiconductor observed by TEM, a grain boundary may be confirmed.

The polycrystalline oxide semiconductor has a plurality of crystal grains, and the plurality of crystal grains are sometimes aligned differently. In addition, polycrystalline oxide semiconductors are analyzed using an XRD device and using an out-of-plane method, sometimes with one or more peaks. For example, in a polycrystalline IGZO film, a peak indicating that the alignment 2θ is in the vicinity of 31° or a plurality of peaks indicating a plurality of alignments may occur. Further, in a pattern obtained by diffraction of electrons in a polycrystalline oxide semiconductor, spots are sometimes observed.

Since polycrystalline oxide semiconductors have high crystallinity, they sometimes have a high electron mobility. Therefore, a transistor in which a polycrystalline oxide semiconductor is used for a channel formation region has a high field effect mobility. Note that polycrystalline oxide semiconductors sometimes cause segregation of impurities at grain boundaries. Further, the grain boundary of the polycrystalline oxide semiconductor becomes a defect level. Since the grain boundary of the polycrystalline oxide semiconductor sometimes becomes a carrier generation source and a trap level, a polycrystalline oxide semiconductor is sometimes used for channel formation as compared with a transistor in which CAAC-OS is used for a channel formation region. The electrical characteristics of the transistor in the region vary greatly and the reliability is low.

The polycrystalline oxide semiconductor can be formed using a high temperature heat treatment or a laser treatment.

The oxide semiconductor film can be, for example, in a microcrystalline state. Note It is intended that an oxide semiconductor including microcrystals is referred to as a microcrystalline oxide semiconductor.

In the image of the microcrystalline oxide semiconductor observed by TEM, the crystal portion may not be clearly confirmed. In many cases, the size of the crystal portion contained in the microcrystalline oxide semiconductor layer is 1 nm or more and 100 nm or less, or 1 nm or more and 10 nm or less. In particular, crystallites of 1 nm or more and 10 nm or less are referred to as nanocrystals (nc: nanocrystals). An oxide semiconductor having a nanocrystal is referred to as nc-OS (nanocrystalline Oxide Semiconductor). Further, in the image of the nc-OS observed by TEM, the boundary between the crystal portion and the crystal portion may not be clearly confirmed. Further, in the image of nc-OS observed by TEM, since there is no clear grain boundary, segregation of impurities is rarely generated. In addition, nc-OS does not have a clear grain boundary, so the defect state density rarely becomes high. In addition, nc-OS does not have a clear grain boundary, so the reduction in electron mobility is small.

The nc-OS sometimes has a periodic arrangement of atoms in a minute region (for example, a region of 1 nm or more and 10 nm or less). Further, since nc-OS has no regularity between the crystal portion and the crystal portion, the periodicity of the atomic arrangement may not be observed macroscopically, or long-range order may not be observed. Therefore, depending on the analysis method, nc-OS and amorphous oxide semiconductor may not be distinguished. For example, when an XRD apparatus is used and the nc-OS is analyzed by an Out-of-plane method in which the electron beam diameter is larger than that of the crystal portion, a peak indicating the alignment may not be detected. Further, in the electron diffraction pattern obtained by using nc-OS having an electron beam diameter larger than that of the crystal portion (for example, 20 nm Φ or more or 50 nm Φ or more), a halo pattern may be observed. In addition, nc-OS is making Spots may be observed in a nanobeam electron diffraction pattern whose electron beam diameter is the same as that of the crystal portion or smaller than the crystal portion (for example, 10 nm Φ or less or 5 nm Φ or less). Further, in the nanobeam electron diffraction pattern of the nc-OS, a region having a high luminance such as a circle may be observed. Further, in the nanobeam electron diffraction pattern of nc-OS, a plurality of spots are sometimes observed in this region.

FIG. 10B is an example of a nanobeam electron diffraction pattern of a sample including nc-OS. Here, the sample was cut along a direction perpendicular to the surface on which the nc-OS was formed, and it was flaky to have a thickness of about 40 nm. Further, an electron beam having an electron beam diameter of 1 nm Φ is incident here from a direction perpendicular to the cross section of the sample. As can be seen from FIG. 10B, a region having a high luminance such as a circle can be observed in the nanobeam electron diffraction pattern of the nc-OS, and a plurality of spots are observed in the region.

Since the nc-OS sometimes has a periodic arrangement of atoms in a minute region, its defect state density is lower than that of an amorphous oxide semiconductor. Note that since there is no regularity between the crystal portion of the nc-OS and the crystal portion, the density of the defect state of the nc-OS is sometimes higher than that of the CAAC-OS.

Therefore, compared to CAAC-OS, sometimes the carrier density of nc-OS is higher. An oxide semiconductor having a higher carrier density sometimes has a higher electron mobility. Therefore, a transistor in which nc-OS is used for a channel formation region sometimes has a high field effect mobility. Note that since the density of the defect state of the nc-OS is higher than that of the CAAC-OS, the density of the trap state is also high. Therefore, the electrical characteristics of the transistor in which the nc-OS is used for the channel formation region are sometimes changed as compared with the transistor in which CAAC-OS is used for the channel formation region, and Less dependent. Note that since nc-OS can be formed even if a large amount of impurities are contained, nc-OS is more easily formed than CAAC-OS, and may be appropriately used depending on the use. Further, the nc-OS may be formed by a film formation method such as a sputtering method using an AC power source. Since a sputtering method using an AC power source can form a film uniformly on a large-sized substrate, the productivity of a semiconductor device having a transistor in which an nc-OS is used for a channel formation region is high.

The oxide semiconductor may include an amorphous portion. Note that an oxide semiconductor including an amorphous portion is referred to as an amorphous oxide semiconductor. The amorphous oxide semiconductor has an disordered atomic arrangement and does not have a crystal portion. Alternatively, the amorphous oxide semiconductor has an amorphous state like quartz, and its atomic arrangement has no regularity.

For example, in an image of an amorphous oxide semiconductor observed by TEM, a crystal portion may not be observed.

For example, when an amorphous oxide semiconductor is analyzed by an out-of-plane method using an XRD apparatus, a peak indicating alignment may not be detected. Further, in the pattern obtained by diffraction of electrons in the amorphous oxide semiconductor, a halo pattern is sometimes observed. Further, in the pattern obtained by diffraction of the nano-beam electrons by the amorphous oxide semiconductor, no spots are observed, and a halo pattern is observed.

The amorphous oxide semiconductor can be formed by containing impurities such as hydrogen at a high concentration. Therefore, the amorphous oxide semiconductor is an oxide semiconductor containing a high concentration of impurities.

When a high concentration of impurities is contained in the oxide semiconductor, A defect level such as an oxygen defect is sometimes formed in an oxide semiconductor. Therefore, the defect level of the amorphous oxide semiconductor having a high impurity concentration is high. Further, since the amorphous oxide semiconductor has low crystallinity, the density of defect states is higher than that of CAAC-OS or nc-OS.

Therefore, the amorphous oxide semiconductor sometimes has a higher carrier density than the nc-OS. Therefore, a transistor in which an amorphous oxide semiconductor is used for a channel formation region sometimes becomes a normally-on electrical property. Therefore, it can sometimes be suitably used for a transistor that requires a normally-on electrical characteristic. Since the density of the defect state of the amorphous oxide semiconductor is high, the density of the trap state is also high. Therefore, sometimes the electrical characteristics of the transistor using the amorphous oxide semiconductor for the channel formation region are largely changed and the reliability is lower than that of the transistor in which CAAC-OS or nc-OS is used for the channel formation region. . Note that since an amorphous oxide semiconductor can be formed by a film formation method which may contain a large amount of impurities, the amorphous oxide semiconductor is easily formed, and may be suitably used depending on the application. For example, a film forming method such as a spin coating method, a sol-gel method, a dipping method, a spraying method, a screen printing method, a contact printing method, an inkjet method, a roll coating method, or a mist CVD method can be used. To form an amorphous oxide semiconductor. Therefore, a semiconductor device having a transistor in which an amorphous oxide semiconductor is used for a channel formation region is highly productive.

Further, the oxide semiconductor may be a mixed film of two or more kinds including CAAC-OS, polycrystalline oxide semiconductor, microcrystalline oxide semiconductor, and amorphous oxide semiconductor. The mixed film, for example, sometimes includes a region of an amorphous oxide semiconductor, a region of a microcrystalline oxide semiconductor, and a polycrystal. Two or more regions in the region of the oxide semiconductor and the region of the CAAC-OS. Further, the mixed film may have a laminated structure of, for example, a region of an amorphous oxide semiconductor, a region of a microcrystalline oxide semiconductor, a region of a polycrystalline oxide semiconductor, and a region of two or more regions of a CAAC-OS.

The oxide semiconductor can be, for example, in a single crystal state. Note that an oxide semiconductor including a single crystal is referred to as a single crystal oxide semiconductor.

For example, since the impurity concentration of the single crystal oxide semiconductor is low and the density of the defect state is low (less oxygen defects), the carrier density can be lowered. Therefore, a transistor in which a single crystal oxide semiconductor is used for a channel formation region rarely becomes a normally-on electrical property. Further, since the defect state density of the single crystal oxide semiconductor is low, the trap state density sometimes becomes low. Therefore, the crystal characteristics of the transistor in which the single crystal oxide semiconductor is used in the channel formation region are small, and the transistor is highly reliable.

Oxide semiconductors sometimes have fewer defects and higher density. Further, the oxide semiconductor sometimes has a higher crystallinity and a higher density. Further, the lower the concentration of an impurity such as an oxide semiconductor such as hydrogen, the higher the density. Further, the density of the single crystal oxide semiconductor is sometimes higher than the density of the CAAC-OS. In addition, the density of CAAC-OS is sometimes higher than that of microcrystalline oxide semiconductors. Further, the density of the polycrystalline oxide semiconductor is sometimes higher than that of the microcrystalline oxide semiconductor. Further, the density of the microcrystalline oxide semiconductor is sometimes higher than that of the amorphous oxide semiconductor.

Further, in order to form a CAAC-OS film, the following conditions are preferably employed.

By reducing the mixing of impurities during film formation, it is possible to suppress impurities Damage to the crystalline state caused by the quality. For example, the concentration of impurities (hydrogen, water, carbon dioxide, nitrogen, etc.) present in the film forming chamber may be reduced. Further, the concentration of impurities in the film forming gas may be lowered. Specifically, a film forming gas having a dew point of -80 ° C or lower, preferably -100 ° C or lower is used.

Further, by increasing the heating temperature (for example, the substrate heating temperature) of the surface on which the CAAC-OS film is formed during film formation, migration of the sputtered particles occurs after the sputtered particles reach the surface on which the CAAC-OS film is formed. Specifically, the film formation is carried out in a state where the surface temperature at which the CAAC-OS film is formed is set to 100° C. or higher and 740° C. or lower, preferably 150° C. or higher and 500° C. or lower.

Further, it is preferable to reduce the plasma damage at the time of film formation by increasing the proportion of oxygen in the film forming gas and optimizing the electric power. The proportion of oxygen in the film forming gas is set to 30 vol.% or more, preferably 100 vol.%.

Next, an In-Ga-Zn-O compound target is shown as an example of a sputtering target.

The InO _X powder, the GaO _Y powder, and the ZnO _Z powder are mixed at a predetermined molar number, and subjected to a pressure treatment, and then heat-treated at a temperature of 1000 ° C or higher and 1500 ° C or lower to obtain a polycrystal. In-Ga-Zn-based metal oxide target. Further, the pressurization treatment may be performed while cooling (cooling) or heating. In addition, X, Y and Z are arbitrary positive numbers. Here, the predetermined molar ratio of the InO _x powder, the GaO _Y powder, and the ZnO _Z powder is, for example, 2:2:1, 8:4:3, 3:1:1, 1:1:1, 4:2 : 3 or 3:1:2 and so on. In addition, the kind of the powder and its mixed molar ratio can be appropriately changed depending on the sputtering target to be produced.

Here, Table 1 shows a comparison between an oxide semiconductor (denoted as OS) and germanium (expressed as Si) in a crystalline state.

Examples of the crystal state of the oxide semiconductor include amorphous oxide semiconductors (a-OS, a-OS: H), microcrystalline oxide semiconductors (nc-OS, μc-OS), and polycrystalline oxidation shown in Table 1. Semiconductor (polycrystalline OS), continuous crystalline oxide semiconductor (CAAC-OS), single crystal oxide semiconductor (single crystal OS), and the like. Further, examples of the crystal state of ruthenium include amorphous ruthenium (a-Si, a-Si: H), microcrystalline ruthenium (nc-Si, μc-Si), and polycrystalline iridium (polycrystalline Si) shown in Table 1, Continuous crystallization 矽 (CG (Continuous Grain) Si), single crystal germanium (single crystal Si), and the like.

When an electron diffraction (electron beam diffraction) in which an electron beam diameter converges to an electron beam of 10 nm Φ or less is used for an oxide semiconductor in each crystal state, an electron diffraction pattern (nano) shown below is observed. Beam electron diffraction pattern). A halo pattern (also referred to as a halo or halo) is observed in the amorphous oxide semiconductor. Spots or/and ring patterns were observed in the microcrystalline oxide semiconductor. Spots were observed in the polycrystalline oxide semiconductor. Spots were observed in the continuous crystalline oxide semiconductor. Spots were observed in the single crystal oxide semiconductor.

Further, it is understood from the nanobeam electron diffraction pattern that the fineness of the crystal portion of the microcrystalline oxide semiconductor is from nanometer (nm) to micrometer (μm). Since the polycrystalline oxide semiconductor has a grain boundary between the crystal portion and the crystal portion, it is known that the boundary is discontinuous. Since the continuous crystalline oxide semiconductor does not have a boundary between the crystal portion and the crystal portion, it is understood that the crystal portion is continuous.

The density of the oxide semiconductor in each crystal state will be described. The density of the amorphous oxide semiconductor is low. The density of the microcrystalline oxide semiconductor is moderate. The density of the continuous crystalline oxide semiconductor is high. That is, the density of the continuous crystalline oxide semiconductor is higher than that of the microcrystalline oxide semiconductor, and the density of the microcrystalline oxide semiconductor is higher than that of the amorphous oxide semiconductor.

The characteristics of the density of states (DOS) present in the oxide semiconductor in each crystal state are explained. The DOS of an amorphous oxide semiconductor is high. The DOS of the microcrystalline oxide semiconductor is slightly lower. The DOS of continuous crystalline oxide semiconductors is low. The DOS of single crystal oxide semiconductor is extremely low. Also That is to say, the DOS of the single crystal oxide semiconductor is lower than that of the continuous crystalline oxide semiconductor, the DOS of the continuous crystalline oxide semiconductor is lower than that of the microcrystalline oxide semiconductor, and the DOS of the microcrystalline oxide semiconductor is lower than that of the amorphous oxide semiconductor.

Further, the oxide semiconductor film may have a structure in which a plurality of oxide semiconductor films are laminated. For example, as in the transistor shown in FIG. 9A, the semiconductor film may be a laminate of the first oxide semiconductor film 188a and the second oxide semiconductor film 188b. Metal oxides having different atomic ratios may be used for the first oxide semiconductor film 188a and the second oxide semiconductor film 188b. For example, an oxide containing two metals, an oxide containing three metals, or an oxide containing four metals may be used as one oxide semiconductor film, and being used as another oxide semiconductor film may be different from an oxide semiconductor film. An oxide of two metals, an oxide comprising three metals or an oxide comprising four metals.

Further, the constituent elements of the first oxide semiconductor film 188a and the second oxide semiconductor film 188b may be the same, and the atomic ratios of the two may be different. For example, the atomic ratio of one oxide semiconductor film can be set to In:Ga:Zn=3:1:2, and the atomic ratio of another oxide semiconductor film can be set to In:Ga:Zn=1:1 :1. Further, the atomic ratio of one oxide semiconductor film may be set to In:Ga:Zn=2:1:3, and the atomic ratio of the other oxide semiconductor film may be set to In:Ga:Zn=1: 3:2. The atomic ratio of one oxide semiconductor film may be set to In:Ga:Zn=1:1:1, and the atomic ratio of the other oxide semiconductor film may be set to In:Ga:Zn=1:3: 2. Can also be an oxide half The atomic ratio of the conductor film is set to In:Ga:Zn=1:1:1, and the atomic ratio of the other oxide semiconductor film is set to In:Ga:Zn=1:6:4. It is also possible to set the atomic ratio of one oxide semiconductor film to In:Ga:Zn=1:1:1, and the atomic ratio of the other oxide semiconductor film to In:Ga:Zn=1:9: 6. In addition, the atomic ratio of each oxide semiconductor film includes a variation of ±20% of the above atomic ratio as an error.

At this time, the atomic ratio of In and Ga of the oxide semiconductor film on the side (channel side) closer to the gate electrode in one oxide semiconductor film and the other oxide semiconductor film is set to In In Ga, and the atomic ratio of In and Ga of the oxide semiconductor film on the side farther from the gate electrode (on the back channel side) is set to In<Ga, a transistor having a high field effect mobility can be manufactured. On the other hand, by setting the atomic ratio of In and Ga of the oxide semiconductor film on the channel side to In<Ga, the atomic ratio of In and Ga of the oxide semiconductor film on the back channel side is set to In. Ga can reduce the variation of the critical time of the transistor or the variation of the threshold voltage due to the reliability test.

Further, the semiconductor film of the transistor may have a three-layer structure composed of the first oxide semiconductor film to the third semiconductor film. At this time, the constituent elements of the first oxide semiconductor film to the third oxide semiconductor film may be made the same, and their atomic ratios may be different from each other. The structure of a transistor in which a semiconductor film is three layers will be described with reference to FIG. 9B.

The transistor shown in FIG. 9B has a first oxide semiconductor film 199a, a second oxide semiconductor film 199b, and a third oxide semiconductor film 199c laminated in this order from the gate insulating film 127 side. As the material constituting the first oxide semiconductor film 199a and the third oxide semiconductor film 199c, it is possible to use InM _1x Zn _y O _z (x) 1, y>1, z>0, M ₁ =Ga, Hf, etc.). Note that in the case where Ga is contained in the material constituting the first oxide semiconductor film 199a and the third oxide semiconductor film 199c, when the ratio of Ga contained is large, it is clear that InM _1x Zn _y O _z can be used. When X in the material indicated is larger than 10, powder may be generated at the time of film formation, which is not suitable.

Further, the material constituting the second oxide semiconductor film 199b can be used with InM _2x Zn _y O _z (x 1,y The material represented by x, z>0, M ₂ =Ga, Sn, etc.).

The materials of the first, second, and third oxide semiconductor films are appropriately selected such that the conduction band bottom of the second oxide semiconductor film 199b and the conduction band bottom and the third oxide semiconductor of the first oxide semiconductor film 199a are formed. The bottom of the film 199c is compared to the well structure that is the deepest from the vacuum level.

Further, bismuth or carbon of one of the Group 14 elements in the oxide semiconductor film sometimes causes formation of a donor energy level. Thereby, when germanium or carbon is contained in the oxide semiconductor film, the oxide semiconductor film becomes n-type. Therefore, it is preferable to form each oxide semiconductor film so that the concentration of ruthenium and carbon is 3 × 10 ¹⁸ /cm ³ or less, preferably 3 × 10 ¹⁷ /cm ³ or less. In particular, in order to prevent a large amount of the Group 14 element from being mixed into the second oxide semiconductor film 199b, it is preferable to sandwich or surround the first oxide semiconductor film 199a and the third oxide semiconductor film 199c to form a carrier path. The second oxide semiconductor film 199b. In other words, the first oxide semiconductor film 199a and the third oxide semiconductor film 199c may be referred to as a barrier film, and the barrier film prevents the Group 14 element such as germanium or carbon from being mixed into the second oxide semiconductor film 199b.

For example, the first oxide semiconductor film 199a and the third oxide may be formed using an oxide semiconductor film having an atomic ratio of In:Ga:Zn=1:3:2 or 1:6:4 or 1:9:6. The semiconductor film 199c, and the second oxide semiconductor film 199b can be formed using an oxide semiconductor film having an atomic ratio of In:Ga:Zn=1:1:1 or 3:1:2.

Alternatively, a three-layer structure in which a film is formed by using an oxide semiconductor film having an atomic ratio of In:Ga:Zn=1:3:2 to form the first oxide semiconductor film 199a; using an atomic ratio of In may be employed. :Ga:Zn = 1:1:1 or In:Ga:Zn=3:1:2 oxide semiconductor film to form the second oxide semiconductor film 199b; and using an atomic ratio of In:Ga:Zn=1 :6:4 or 1:9:6 oxide semiconductor film to form the third oxide semiconductor film 199c.

Since the constituent elements of the first to third oxide semiconductor films 199a to 199c are the same, the defect state density (trap state density) of the interface between the second oxide semiconductor film 199b and the first oxide semiconductor film 199a low. In detail, the defect state density (trap state density) is lower than the defect state density of the interface between the gate insulating film 127 and the first oxide semiconductor film 199a. Thereby, by laminating the oxide semiconductor film as described above, it is possible to reduce the variation of the period of time of the transistor or the variation of the threshold voltage due to the reliability test.

In addition, the second oxide semiconductor film 199b is made by appropriately selecting the materials of the first, second, and third oxide semiconductor films. The conduction band bottom constitutes a well structure which is the deepest from the vacuum level of the conduction band bottom of the first oxide semiconductor film 199a and the conduction band bottom of the third oxide semiconductor film 199c, and can improve the field effect mobility of the transistor. It is also possible to reduce the variation of the critical time of the transistor or the variation of the threshold voltage due to the reliability test.

Further, an oxide semiconductor having different crystallinity may be used as the first oxide semiconductor film 199a to the third oxide semiconductor film 199c. That is to say, a structure in which a single crystal oxide semiconductor, a polycrystalline oxide semiconductor, a microcrystalline (nanocrystalline) oxide semiconductor, an amorphous oxide semiconductor, and a CAAC-OS film are appropriately combined may be employed. Further, when any one of the first to third oxide semiconductor films 199a to 199c is an amorphous oxide semiconductor, the internal stress and the external stress of the oxide semiconductor film can be alleviated, and the characteristic deviation of the transistor can be lowered. It is also possible to reduce the variation of the critical time of the transistor or the variation of the threshold voltage due to the reliability test.

Further, the second oxide semiconductor film 199b which becomes at least the channel formation region is preferably a CAAC-OS film.

When a conductive material (for example, a metal for a source electrode or a gate electrode) which is easily bonded to oxygen is brought into contact with an oxide semiconductor film, oxygen diffusion in the oxide semiconductor film occurs to conduct electricity which is easily bonded to oxygen. The phenomenon on one side of the material. The higher the temperature, the more pronounced this phenomenon occurs. Since there are several heating processes in the process of the transistor, oxygen defects occur in the region of the oxide semiconductor layer in contact with the source electrode or the drain electrode and the region in the vicinity thereof due to the above phenomenon, and the region becomes n. type. Therefore, the region which becomes n-type can be used as the source or drain of the transistor.

9A and 9B illustrate the above-described n-type region. A boundary 135 indicated by a broken line in the semiconductor film is a boundary between the intrinsic semiconductor region and the n-type semiconductor region, and in the oxide semiconductor, a region in contact with the source electrode or the drain electrode and a region in the vicinity thereof become an n-type region. Note that the boundary 135 is shown schematically, and is sometimes not clear. Further, sometimes the position of the boundary 135 is also different from the position shown.

Note that this embodiment can be combined as appropriate with other embodiments shown in the present specification.

Embodiment 3

In the present embodiment, an electron diffraction pattern and a local energy level of a nanocrystalline oxide semiconductor film which can be used in one embodiment of the present invention will be described.

The nanocrystalline oxide semiconductor film is an oxide semiconductor film in which an electron diffraction pattern of electron diffraction (nanobeam electron diffraction) having an electron beam diameter of 10 nm Φ or less is observed and expressed in an amorphous state. The halo pattern and the regular spots indicating the crystallization state of the specific surface are different and have no directional spots.

Fig. 13A shows a cross-sectional TEM (Transmission Electron Microscopy) image of a nanocrystalline oxide semiconductor film. Further, Fig. 13B shows an electron diffraction pattern measured by nanobeam electron diffraction in point 1 of Fig. 13A, and Fig. 13C shows electron diffraction measured by nanobeam electron diffraction at point 2 of Fig. 13A. Pattern, Figure 13D shows an electronic diffraction pattern measured using nanobeam electron diffraction in point 3 of Figure 13A.

In FIGS. 13A to 13D, as an example of the nanocrystalline oxide semiconductor film, a sample in which a 50 nm thick In-Ga-Zn-based oxide film is formed on a quartz glass substrate is used. The film formation conditions of the nano microcrystalline oxide semiconductor film shown in FIGS. 13A to 13D are as follows: an oxide target using In:Ga:Zn=1:1:1 (atomic ratio); an oxygen atmosphere (flow rate) 45 sccm); pressure is 0.4 Pa; direct current (DC) power is 0.5 kW; and the substrate temperature is room temperature. Then, the formed nanocrystalline oxide semiconductor film is thinned to a width of 100 nm or less (for example, 40 nm ± 10 nm) to obtain a cross-sectional TEM image and an electron diffraction pattern that is diffracted by the nanobeam electrons.

Fig. 13A shows a cross-sectional TEM image of a nanocrystalline oxide semiconductor film taken by a transmission electron microscope ("H-9000NAR" manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 300 kV and a magnification of 2 million times. In addition, FIGS. 13B to 13D show that a nano electron beam is obtained by a transmission electron microscope ("HF-2000" manufactured by Hitachi High-Technologies Corporation) with an acceleration voltage of 200 kV and an electron beam diameter of about 1 nm Φ. Electronic diffraction pattern. Further, the measurement range of the nanobeam electron diffraction when the electron beam diameter is approximately 1 nm Φ is 5 nm Φ or more and 10 nm Φ or less.

As shown in FIG. 13B, a plurality of spots (bright spots) distributed in a circumferential shape were observed in the electron diffraction pattern of the nanocrystalline oxide semiconductor film which was diffracted by the nanobeam electrons. In other words, in the nanocrystalline oxide semiconductor film, a plurality of spots distributed in a circumferential shape (concentric shape) were observed. Alternatively, it can be said that a plurality of spots distributed in a circumferential shape form a plurality of concentric circles.

Further, in FIG. 13C near the center of the thickness direction of FIG. 13D and the nanocrystalline oxide semiconductor film in the vicinity of the interface of the quartz glass substrate, a plurality of spots distributed concentrically as in FIG. 13B were also observed. In Fig. 13C, the distance (radius) from the main spot to the first circumference is 3.88 / nm to 4.93 / nm. When converted to the interplanar spacing, it is 0.203 nm to 0.257 nm.

From the nanobeam electron diffraction pattern of FIGS. 13A to 13D, it is understood that in the nanocrystalline oxide semiconductor film, a plurality of crystal portions having irregular crystal plane alignment and different sizes are mixed.

Next, FIG. 14A shows a planar TEM image of a nanocrystalline oxide semiconductor film. Further, Fig. 14B shows an electron diffraction pattern obtained by measuring the area circled in Fig. 14A by the selection electron diffraction.

In FIGS. 14A and 14B, as an example of the nanocrystalline oxide semiconductor film, a sample in which a 30 nm thick In-Ga-Zn-based oxide film is formed on a quartz glass substrate is used. The film formation conditions of the nanocrystalline oxide semiconductor film shown in FIGS. 14A and 14B are as follows: an oxide target using In:Ga:Zn=1:1:1 (atomic ratio); an oxygen atmosphere (flow rate is used) 45 sccm); pressure is 0.4 Pa; direct current (DC) power is 0.5 kW; and the substrate temperature is room temperature. Then, the sample was thinned to obtain a planar TEM image of the nanocrystalline oxide semiconductor film and an electronic diffraction pattern using electron diffraction.

Fig. 14A shows an acceleration voltage of 300 kV using a transmission electron microscope ("H-9000NAR" manufactured by Hitachi High-Technologies Corporation) And a planar TEM image of a nanocrystalline oxide semiconductor film taken at a magnification of 500,000 times. Further, Fig. 14B is an electron diffraction pattern obtained by electron diffraction of a selected region of 300 nm Φ. Note that when considering the expanded range of the electron beam, the measurement range is 300 nm Φ or more.

As shown in FIG. 14B, in the electron diffraction pattern of the nanocrystalline oxide semiconductor film which is diffracted by the selected region whose measurement range is larger than the diffraction of the electrons of the nanobeam, a halo pattern is observed without observing the use of the nanometer. The beam of electrons diffracts multiple spots observed.

15A to 15C schematically show the distribution of the diffraction intensity in the electron diffraction patterns shown in Figs. 13A to 13D and Figs. 14A and 14B. Fig. 15A is a schematic view showing a distribution of diffraction intensities in the nanobeam electron diffraction pattern shown in Figs. 13B to 13D. Fig. 15B is a schematic view showing the distribution of the diffraction intensity in the selected area electronic diffraction pattern shown in Fig. 14B. In addition, FIG. 15C is a schematic view showing a distribution of diffraction intensity in an electron diffraction pattern of a single crystal structure or a polycrystalline structure.

In FIGS. 15A to 15C, the vertical axis represents the electron diffraction intensity (arbitrary unit) representing the distribution of spots or the like, and the horizontal axis represents the distance from the main spot.

In the single crystal structure or the polycrystalline structure shown in Fig. 15C, spots are observed at positions spaced apart from the main spots by a plane interval (d value) corresponding to the surface of the crystal portion alignment.

On the other hand, as shown in FIGS. 13A to 13D, the plurality of spots observed in the nanobeam electron diffraction pattern of the nanocrystalline oxide semiconductor film have a large width. Therefore, FIG. 15A shows the intensity score of the dispersed state. cloth. Further, it is understood that in the nanobeam electron diffraction pattern, there is a region where the brightness is high, although a clear spot is not formed between the concentric regions.

Further, as shown in FIG. 15B, the electron diffraction intensity distribution in the selected electron diffraction pattern of the nanocrystalline oxide semiconductor film shows a continuous intensity distribution. Since FIG. 15B can be approximated to the result obtained by observing the electron diffraction intensity distribution shown in FIG. 15A in a wide range, it can be considered that the plurality of spots shown in FIG. 15A are overlapped and connected, thereby obtaining a continuous intensity distribution.

As shown in FIGS. 15A to 15C, it is understood that in the nanocrystalline oxide semiconductor film, a plurality of crystal portions having irregular crystal planes and different sizes are mixed together, and the crystal portion is fine to be observed in the selected electron diffraction pattern. Not to the extent of the spots.

In FIGS. 13A to 13D in which a plurality of spots are observed, the nanocrystalline oxide semiconductor film is thinned to 50 nm or less. Further, since the electron beam diameter of the electron beam converges to 1 nm Φ, the measurement range is 5 nm or more and 10 nm or less. Thus, the crystal portion included in the nanocrystalline oxide semiconductor film can be estimated to be at least 50 nm or less, for example, 10 nm or less or 5 nm or less.

Here, FIG. 16 shows a nanobeam electron diffraction pattern of a quartz glass substrate. The measurement conditions of Fig. 16 are the same as those of Figs. 13B to 13D.

As shown in Fig. 16, a halo pattern was observed from a quartz glass substrate having an amorphous structure in which a specific spot was not obtained by diffraction and its luminance continuously changed from the main spot. Like this, there is In the film of an amorphous structure, even if electron diffraction was performed in a very minute region, a plurality of spots having a circumferential distribution as observed in the nanocrystalline oxide semiconductor film were not observed. Therefore, it was confirmed that a plurality of spots in which the distribution observed in FIGS. 13B to 13D is circumferential are peculiar to the nanocrystalline oxide semiconductor film.

Fig. 17 shows an electron diffraction pattern in which the dot 2 shown in Fig. 13A is irradiated with an electron beam having an electron beam diameter converging to about 1 nm Φ for 1 minute, followed by measurement.

In the electronic diffraction pattern shown in Fig. 17, a plurality of spots distributed in a circumferential shape are observed in the same manner as the electronic diffraction pattern shown in Fig. 13C, and there is no measurement between the measurement results shown in Figs. 17 and 13C. Confirm the difference. This means that the crystal portion confirmed in the electron diffraction pattern of FIG. 13C is present when the nanocrystalline oxide semiconductor film is formed, and the crystal portion is not formed by the irradiation of the astringent electron beam.

18A and 18B are partial enlarged views of the cross-sectional TEM image shown in Fig. 13A. Fig. 18A is a cross-sectional TEM image obtained when the vicinity of the point 1 of Fig. 13A (the surface of the nanocrystalline oxide semiconductor film) is observed at a magnification of 8 million times. In addition, FIG. 18B is a cross-sectional TEM image obtained when the vicinity of the point 2 of FIG. 13A (the central portion in the film thickness direction of the nanocrystalline oxide semiconductor film) is observed at a magnification of 8 million times.

The crystal structure in the nanocrystalline oxide semiconductor film cannot be clearly observed from the cross-sectional TEM image shown in Figs. 18A and 18B.

Further, an X-ray diffraction (XRD: X-ray Diffraction) pair is used for FIGS. 13A to 13D and FIGS. 14A and 14B. A sample of the nanocrystalline oxide semiconductor film of the present embodiment formed on the quartz glass substrate was observed for analysis. Fig. 19 shows the results obtained by measuring the XRD spectrum by the out-of-plane method.

In Fig. 19, the vertical axis represents the X-ray diffraction intensity (arbitrary unit), and the horizontal axis represents the diffraction angle 2θ (deg.). Further, an X-ray diffraction device D-8 ADVANCE manufactured by Bruker AXS Co., Ltd. was used for the measurement of the XRD spectrum.

As shown in FIG. 19, a peak due to quartz was observed in the vicinity of 2θ=20° to 23°, but the peak of the crystal portion included in the nanocrystalline oxide semiconductor film could not be confirmed.

As is clear from the results of FIGS. 18A and 18B and FIG. 19, the crystal portion included in the nanocrystalline oxide semiconductor film is a very fine crystal portion.

As described above, in the nanocrystalline oxide semiconductor film of the present embodiment, when the analysis using X-ray diffraction (XRD: X-ray diffraction) having a large measurement range is performed, no peak indicating the alignment is detected, and A halo pattern is observed in an electronic diffraction pattern obtained by diffraction of a selected area having a large measurement range. Therefore, the nanocrystalline oxide semiconductor film of the present embodiment can be said to be the same film as the film having an disordered atomic arrangement. However, by measuring the nanocrystalline oxide semiconductor film by using a beam diameter of an electron beam having a sufficiently small electron beam diameter (for example, 10 nm Φ or less), the obtained nanobeam electron diffraction pattern can be used. Spots (bright spots) were observed. Therefore, it is presumed that the nanocrystalline oxide semiconductor film of the present embodiment is agglomerated in a crystal phase in which a crystal plane is irregularly oriented (for example, a crystal portion having a particle diameter of 10 nm or less, 5 nm or less, or 3 nm or less). And the film formed. Further, a nanocrystalline region containing a very fine crystal portion is included in the entire region in the thickness direction of the nanocrystalline oxide semiconductor film.

Here, the local energy level of the nanocrystalline oxide semiconductor film will be described, and the results obtained by evaluating the nanocrystalline oxide semiconductor film by CPM (Constant Photocurrent Measurement) will also be described.

First, the structure of the measurement sample will be explained.

The measurement sample includes an oxide semiconductor film provided on a glass substrate, a pair of electrodes in contact with the oxide semiconductor film, and an insulating film covering the oxide semiconductor film and a pair of electrodes.

Next, a method of forming the oxide semiconductor film included in the measurement sample will be described.

The first oxide semiconductor film is formed by a sputtering method using a target of In—Ga—Zn oxide (In:Ga:Zn=1:1:1 [atomic ratio]); as a film forming gas 30 sccm of argon gas and 15 sccm of oxygen gas were used; pressure was 0.4 Pa; substrate temperature was room temperature; and 0.5 kW of DC power was applied. Note that the first oxide semiconductor film is a nanocrystalline oxide semiconductor film.

Further, the first oxide semiconductor film was heated in a nitrogen atmosphere at 450 ° C for 1 hour, and then heated in an oxygen atmosphere at 450 ° C for 1 hour to remove hydrogen contained in the first oxide semiconductor film. The treatment and the treatment of supplying oxygen to the first oxide semiconductor film to form a second oxide semiconductor film. Note that the second oxide semiconductor The film is a nanocrystalline oxide semiconductor film.

Next, CPM measurement is performed on the measurement sample including the first oxide semiconductor film and the measurement sample including the second oxide semiconductor film. Specifically, a voltage is applied between a pair of electrodes in contact with the oxide semiconductor film, and in this state, the amount of light irradiated to the surface of the measurement sample between the terminals is adjusted to fix the photocurrent value, and at a desired wavelength The absorption coefficient is obtained from the amount of irradiation light in the range.

11A and 11B show the absorption coefficient of the absorption coefficient resulting from the bandtail from the absorption coefficient obtained by performing CPM measurement on each measurement sample, that is, the absorption coefficient due to the defect. In FIGS. 11A and 11B, the horizontal axis represents the absorption coefficient, and the vertical axis represents the light energy. Further, in the vertical axis of FIGS. 11A and 11B, the conduction band bottom of the oxide semiconductor film was 0 eV, and the valence band top was 3.15 eV. In addition, in FIGS. 11A and 11B, each curve is a curve indicating the relationship between the absorption coefficient and the light energy, and corresponds to the defect level.

Fig. 11A shows a measurement result of a measurement sample including a first oxide semiconductor film in which the absorption coefficient of the defect level is 5.28 × 10 ^-1 cm ^-1 . Fig. 11B shows the measurement results of the measurement sample including the second oxide semiconductor film in which the absorption coefficient of the defect level is 1.75 × 10 ^-2 cm ^-1 .

Therefore, defects included in the oxide semiconductor film can be reduced by heat treatment.

Further, the first oxide semiconductor film and the second oxide semiconductor film were measured for film density by X-ray reflectometry (XRR: X-Ray Reflectometry). The film density of the first oxide semiconductor film was 5.9 g/cm ³ , and the film density of the second oxide semiconductor film was 6.1 g/cm ³ .

Therefore, the film density of the oxide semiconductor film can be increased by heat treatment.

In other words, it is understood that in the oxide semiconductor film, the higher the film density, the less defects are included in the film.

This embodiment can be combined as appropriate with other embodiments shown in the present specification.

Embodiment 4

In the present embodiment, an electronic diffraction pattern and a local energy level of a CAAC-OS film which can be used in one embodiment of the present invention will be described.

The CAAC-OS film used in the present embodiment is formed by using a target containing In—Ga—Zn oxide (In:Ga:Zn=1:1:1 [atomic ratio]) and using oxygen. An In-Ga-Zn-based oxide film formed by a sputtering method of a gas. For details of the method of producing the CAAC-OS film and the like, reference may be made to the first and second embodiments.

Fig. 20 shows a cross-sectional TEM (Transmission Electron Microscope) image of a CAAC-OS film. In addition, FIGS. 21A to 21D show electron diffraction patterns obtained by measurement using electron diffraction in points 1 to 4 of FIG.

The cross-sectional TEM image shown in Fig. 20 was taken by a transmission electron microscope ("H-9000NAR" manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 300 kV and a magnification of 2 million times. In addition, the map The electron diffraction pattern shown in 21A to 21D was obtained by a transmission electron microscope ("HF-2000" manufactured by Hitachi High-Technologies Corporation) with an acceleration voltage of 200 kV and an electron beam diameter of about 1 nm Φ or about 50 nm Φ. Further, an electron diffraction having an electron beam diameter of 10 nm Φ or less is sometimes referred to as a nanobeam electron diffraction. Further, the measurement range of the nano-electronic diffraction when the electron beam diameter is approximately 1 nm Φ is 5 nm Φ or more and 10 nm Φ or less.

21A, 21B, and 21C are electron diffraction patterns in the dot 1 (film surface side), the dot 2 (film center), and the dot 3 (film substrate side) shown in FIG. 20, respectively, and are electrons. The electron diffraction pattern when the beam diameter is set to about 1 nm Φ. 21D is an electron diffraction pattern in the dot 4 (the entire film) shown in FIG. 20, and is an electron diffraction pattern when the electron beam diameter is set to about 50 nmφ.

In the electron diffraction pattern at the point 1 (the surface of the film surface) and the point 2 (the center of the film), although the pattern formed by the spots (bright spots) can be confirmed, the electron diffraction at the point 3 (the side of the film substrate) In the pattern, the pattern is slightly deformed. This means that the crystal state is different in the film thickness direction of the CAAC-OS film. Further, in the electronic diffraction pattern of the dot 4 (the entire film), a pattern formed by spots (bright spots) can be confirmed, whereby the film as a whole can be a CAAC-OS film or a film containing a CAAC-OS film.

Fig. 22 is a photograph enlarging the vicinity of the point 1 (the side of the film surface) in Fig. 20. From the CAAC-OS film to the interface with the yttrium oxynitride film as the interlayer insulating film, a clear lattice image showing the alignment of the CAAC-OS film was confirmed.

23A and 23B are different from those in the observation of FIG. 20, respectively. A cross-sectional TEM photograph of the CAAC-OS film of the CAAC-OS film used in the cross-sectional TEM and an X-ray diffraction spectrum. The CAAC-OS film has various forms, and a peak A indicating a crystal component appears in the vicinity of 2θ = 31° shown in Fig. 23B. In addition, there are cases where the peak does not appear explicitly.

24A to 24D show the results of electronic winding of the electron beam diameter of the electron beam set to 1 nm Φ, 20 nm Φ, 50 nm Φ, and 70 nm Φ in the region indicated by the concentric circles in the CAAC-OS film of FIG. 23A. The result of the shot. When the electron beam diameter of the electron beam was 1 nm Φ, a pattern formed of a clear spot (bright spot) was confirmed in the same manner as in FIGS. 21A and 21B. Increasing the electron beam diameter of the electron beam makes the spots (bright spots) slightly ambiguous, but the diffraction pattern can be confirmed, so that the film as a whole is a CAAC-OS film or a film containing a CAAC-OS film.

25A and 25B are a cross-sectional TEM photograph and an X-ray diffraction spectrum after annealing the CAAC-OS film used in the cross-sectional TEM of FIG. 23A at 450 ° C, respectively.

26A to 26D show the results of electron winding around the electron beam diameter of the electron beam set to 1 nm Φ, 20 nm Φ, 50 nm Φ, and 70 nm Φ in the region indicated by the concentric circles in the CAAC-OS film of Fig. 25A. The result of the shot. As in the results shown in Figs. 24A to 24D, when the electron beam diameter of the electron beam was 1 nmΦ, a pattern formed by a clear spot (bright spot) was confirmed. Increasing the electron beam diameter of the electron beam makes the spots (bright spots) slightly ambiguous, but the diffraction pattern can be confirmed, so that the film as a whole is a CAAC-OS film or a film containing a CAAC-OS film.

27A and 27B are cross-sectional TEM photographs and X-rays of a CAAC-OS film different from the CAAC-OS film used in the cross-sectional TEM of FIG. 20 and the CAAC-OS film used in the cross-sectional TEM of FIG. 23A, respectively. Diffraction spectrum. The CAAC-OS film has various forms, and it is possible to appear a peak A indicating a crystal component in the vicinity of 2θ = 31° shown in Fig. 27B, and a peak B due to a crystal structure of a spinel type.

28A to 28D show the results of electron winding around the electron beam diameter of the electron beam set to 1 nm Φ, 20 nm Φ, 50 nm Φ, and 90 nm Φ in the region shown by the concentric circles in the CAAC-OS film of Fig. 27A. The result of the shot. When the electron beam diameter of the electron beam was 1 nm Φ, a pattern formed by a clear spot (bright spot) was confirmed. Increasing the electron beam diameter of the electron beam makes the spots (bright spots) slightly ambiguous, but the diffraction pattern can be confirmed. Further, when the electron beam diameter of the electron beam was 90 nmΦ, more clear spots (bright spots) were confirmed. From this, it can be said that the entire film is a CAAC-OS film or a film containing a CAAC-OS film.

Next, the local energy level of the CAAC-OS film will be explained. Here, the results obtained by evaluating the CAAC-OS film by CPM (Constant photocurrent method) are also described.

First, the structure of a sample for performing CPM measurement will be described.

The measurement sample includes an oxide semiconductor film provided on a glass substrate, a pair of electrodes in contact with the oxide semiconductor film, and an insulating film covering the oxide semiconductor film and a pair of electrodes.

Next, a method of forming the oxide semiconductor film included in the measurement sample will be described.

An oxide semiconductor film was formed by a sputtering method using a target of In-Ga-Zn oxide (In:Ga:Zn=1:1:1 [atomic ratio]); 30 sccm was used as a film forming gas. Argon gas, 15 sccm of oxygen gas; pressure of 0.4 Pa; substrate temperature of 400 ° C; application of 0.5 kW of DC power. Then, it is heated in a nitrogen atmosphere at 450 ° C for 1 hour, and then heated in an oxygen atmosphere at 450 ° C for 1 hour to perform treatment for removing hydrogen contained in the oxide semiconductor film and supplying oxygen to the oxide semiconductor film. deal with. Note that this oxide semiconductor film is a CAAC-OS film.

Next, CPM measurement was performed on the measurement sample including the oxide semiconductor film. Specifically, a voltage is applied between a pair of electrodes in contact with the oxide semiconductor film, and the amount of light irradiated to the surface of the sample between the terminals is adjusted in this state to fix the photocurrent value, and in the range of the desired wavelength The absorption coefficient is obtained from the amount of illumination light.

Fig. 12 shows an absorption coefficient due to the absorption coefficient of the tail from the absorption coefficient obtained by performing CPM measurement on each measurement sample, that is, an absorption coefficient resulting from the defect. In Fig. 12, the horizontal axis represents the absorption coefficient, and the vertical axis represents the light energy. Further, in the vertical axis of Fig. 12, the conduction band bottom of the oxide semiconductor film was 0 eV, and the valence band top was 3.15 eV. In addition, in FIG. 12, the curve shows the relationship between the absorption coefficient and the light energy, which corresponds to the defect level.

In the graph shown in Fig. 12, the absorption coefficient of the defect level is 5.86 × 10 ^-4 cm ^-1 . That is, the CAAC-OS film has a lower energy absorption coefficient of a defect level of less than 1 × 10 ^-3 /cm, preferably less than 1 × 10 ^-4 /cm.

Further, the oxide semiconductor film was measured for film density by X-ray reflectometry (XRR). The film density of the oxide semiconductor film was 6.3 g/cm ³ , that is, the film density of the CAAC-OS film was high.

This embodiment can be combined as appropriate with other embodiments shown in the present specification.

Embodiment 5

A semiconductor device (display device) having a display function can be manufactured by using the transistor and the capacitor element exemplified in the above embodiments. Further, a system-on-panel can be formed by forming part or all of the driving circuit including the transistor on the same substrate together with the pixel portion. In the present embodiment, an example of a display device using the transistor described in the above embodiment will be described with reference to FIGS. 29A to 31C. In addition, FIG. 30 is a cross-sectional view showing a cross-sectional structure along the M-N chain line in FIG. 29B. Further, only a part of the structure of the pixel portion is shown in FIG.

In FIG. 29A, a sealing material 905 is provided in such a manner as to surround the pixel portion 902 provided on the first substrate 901, and sealing is performed using the second substrate 906. In FIG. 29A, a second driving circuit 903 and a first substrate formed on a separately prepared substrate using a single crystal semiconductor or a polycrystalline semiconductor are mounted in a region on the first substrate 901 different from a region surrounded by the sealing material 905. Drive circuit 904. In addition, supplied to the second drive Various signals and potentials of the path 903, the first driving circuit 904, or the pixel portion 902 are supplied by FPC (Flexible Print Circuit) 918a and FPC 918b.

Note that the first driving circuit 904 has a function of a scanning line driving circuit. Further, the second drive circuit 903 has a function of a signal line drive circuit.

In FIGS. 29B and 29C, a sealing material 905 is provided in such a manner as to surround the pixel portion 902 and the first driving circuit 904 provided on the first substrate 901. Further, a second substrate 906 is provided on the pixel portion 902 and the first driving circuit 904. Therefore, the pixel portion 902 and the first driving circuit 904 are sealed together with the display element by the first substrate 901, the sealing material 905, and the second substrate 906. In FIGS. 29B and 29C, a second driving circuit 903 which is separately formed using a single crystal semiconductor or a polycrystalline semiconductor is mounted in a region on the first substrate 901 which is different from a region surrounded by the sealing material 905. In FIGS. 29B and 29C, various signals and potentials supplied to the second driving circuit 903, the first driving circuit 904, or the pixel portion 902 are supplied from the FPC 918.

Further, FIGS. 29B and 29C illustrate an example in which the second driving circuit 903 is separately formed and mounted to the first substrate 901, but is not limited to this configuration. The first driving circuit may be separately formed and mounted, or only a part of the second driving circuit or a part of the first driving circuit may be separately formed and mounted.

In addition, there is no particular limitation on the connection method of the separately formed driving circuit, and COG (Chip On Glass) can be used. Glass bonding method, wire bonding method, or TCP (Tape Carrier Package). 29A is an example in which the second driving circuit 903 and the first driving circuit 904 are mounted by the COG method, FIG. 29B is an example in which the second driving circuit 903 is mounted by the COG method, and FIG. 29C is a second driving by the TCP method. An example of circuit 903.

Further, the display device includes a panel in which the display element is in a sealed state and a module in which an IC such as a controller or the like is mounted.

Note that the display device in this specification refers to an image display device or a display device. In addition, it can also be used as a light source (including a lighting device) instead of a display device. In addition, the display device further includes: a module mounted with a connector such as FPC or TCP; a module provided with a printed circuit board at the end of the TCP; or directly mounting the IC (integrated circuit) to the display by a COG method The module of the component.

Further, the pixel portion and the first driving circuit provided on the first substrate have a plurality of transistors, and the transistor described in the above embodiment can be applied.

As the display element provided in the display device, a liquid crystal element, a light-emitting element, or the like can be used. As an example of the liquid crystal element, there is an element that controls the transmission or non-transmission of light by the optical modulation effect of the liquid crystal. The element can be composed of a pair of electrodes and a liquid crystal layer. Further, the optical modulation of the liquid crystal is controlled by an electric field applied to the liquid crystal (including a transverse electric field, a longitudinal electric field, or an oblique electric field). In addition, as an example of the liquid crystal element, nematic liquid crystal, cholesterol phase liquid crystal, smectic liquid crystal, discotic liquid crystal, thermotropic liquid crystal, lyotropic liquid crystal, low molecular liquid crystal, and high are mentioned. Molecular liquid crystal, polymer dispersed liquid crystal (PDLC), ferroelectric liquid crystal, antiferroelectric liquid crystal, main chain type liquid crystal, side chain type polymer liquid crystal, banana type liquid crystal, and the like. Further, as a driving method of the liquid crystal, a TN (Twisted Nematic) mode, an STN (Super Twisted Nematic) mode, an IPS (In-Plane-Switching) mode, and an FFS ( Fringe Field Switching mode, MVA (Multi-domain Vertical Alignment) mode, PVA (Patterned Vertical Alignment) mode, ASV (Advanced Super View) mode, ASM (Axially Symmetric aligned Micro-cell) mode, OCB (Optically Compensated Birefringence) mode, ECB (Electrically Controlled Birefringence) mode, FLC (Ferroelectric Liquid Crystal: Iron) Electro-liquid crystal mode, AFLC (AntiFerroelectric Liquid Crystal) mode, PDLC (Polymer Dispersed Liquid Crystal) mode, PNLC (Polymer Network Liquid Crystal) mode, guest-host mode , Blue Phase mode, etc. However, it is not limited thereto, and various liquid crystal elements and their driving methods can be used as the liquid crystal element and its driving method. The light-emitting element includes, in its category, an element that controls brightness by current or voltage, and specifically includes an inorganic EL (Electro Luminescence) element, an organic EL element, and the like. In addition, it is also possible to apply an electronic ink or the like to change the contrast due to electrical action. Show media. Fig. 30 shows an example of a liquid crystal display device using a liquid crystal element as a display element.

Figure 30 is a cross-sectional view showing a vertical electric field type liquid crystal display device. The liquid crystal display device includes a connection terminal electrode 915 and a terminal electrode 916, and the connection terminal electrode 915 and the terminal electrode 916 are electrically connected to a terminal of the FPC 918 by an anisotropic conductive agent 919.

The connection terminal electrode 915 is formed of the same conductive film as the first electrode 930, and the terminal electrode 916 is formed of the same conductive film as the source electrode and the drain electrode of the transistors 910 and 911.

Further, the pixel portion 902 provided on the first substrate 901, the first driving circuit 904 includes a plurality of transistors, and the transistor 910 included in the pixel portion 902 and the transistor 911 included in the first driving circuit 904 are shown. An insulating film 924 corresponding to the insulating film 129, the insulating film 131, and the insulating film 132 shown in the first embodiment is provided on the transistor 910 and the transistor 911. Further, in order to improve flatness, an insulating film 934 is provided on the insulating film 924. Further, the insulating film 923 is a nitride insulating film.

In the present embodiment, as the transistor 910, the transistor provided in the pixel 101 shown in the above-described first embodiment can be applied. As the transistor 911, the transistor provided in the first driving circuit 104 shown in the above-described first embodiment can be applied. Note that, as the transistor 911, a structure in which the conductive film 917 is provided is exemplified, but a structure in which the conductive film 917 is not provided may be employed.

Further, the capacitor element 936 is formed using the oxide semiconductor film 927, the insulating film 924, the insulating film 934, and the first electrode 930. this Further, the oxide semiconductor film 927 is electrically connected to the capacitor line 929. The capacitance line 929 is formed using the same conductive film as the gate electrodes of the transistor 910 and the transistor 911. Note that the capacitance element shown in Embodiment 1 is shown here as the capacitance element 936. However, the capacitance element shown in the other embodiment may be used as appropriate.

The transistor 910 provided in the pixel portion 902 is electrically connected to the display element to constitute a display panel. The display element is not particularly limited as long as it can be displayed, and various display elements can be used.

The liquid crystal element 913 as a display element includes a first electrode 930, a second electrode 931, and a liquid crystal layer 908. Further, an insulating film 932 and an insulating film 933 serving as an alignment film are provided so as to sandwich the liquid crystal layer 908. Further, the second electrode 931 is disposed on the side of the second substrate 906, and the first electrode 930 and the second electrode 931 are overlapped via the liquid crystal layer 908.

The first electrode 930 and the second electrode 931 (also referred to as a pixel electrode, a common electrode, a counter electrode, and the like) provided to apply a voltage to the display element may be based on the direction in which the light is taken out, the position of the electrode, and the pattern structure of the electrode. Choose light transmission or reflectivity.

The first electrode 930 and the second electrode 931 can be made of the same material as the pixel electrode 121 shown in the first embodiment.

Further, the spacer 935 is a columnar spacer obtained by selectively etching the insulating film, and it is provided to control the interval (cell gap) between the first electrode 930 and the second electrode 931. In addition, spherical spacers can also be used.

When a liquid crystal element is used as a display element, it can be used Thermotropic liquid crystal, low molecular liquid crystal, polymer liquid crystal, polymer dispersed liquid crystal, ferroelectric liquid crystal, antiferroelectric liquid crystal, and the like. The liquid crystal material exhibits a cholesterol phase, a smectic phase, a cubic phase, a chiral nematic phase, and isotropic in accordance with conditions.

Further, a liquid crystal which does not use an alignment film and exhibits a blue phase can also be used. The blue phase is one of the liquid crystal phases which, when the temperature of the liquid crystal of the cholesterol phase is raised, is present immediately before the transition from the cholesterol phase to the isotropic phase. Since the blue phase appears only in a narrow temperature range, the liquid crystal composition of the mixed chiral agent is used for the liquid crystal layer in order to improve the temperature range. Further, since the alignment film is made of an organic resin containing hydrogen or water, it is possible to lower the electrical characteristics of the transistor of the semiconductor device of one embodiment of the present invention. Then, by using the blue phase as the liquid crystal layer, the semiconductor device of one embodiment of the present invention can be manufactured without using an organic resin, and a highly reliable semiconductor device can be obtained.

The first substrate 901 and the second substrate 906 are fixed by a sealing material 925. As the sealing material 925, an organic resin such as a thermosetting resin or a photocurable resin can be used. In addition, the sealing material 925 is in contact with the insulating film 924. Further, the sealing material 925 corresponds to the sealing material 905 shown in FIGS. 29A to 29C.

The sealing material 925 is disposed on the insulating film 924. Further, an insulating film 934 is disposed inside the sealing material 925. The uppermost layer of the insulating film 924 is a nitride insulating film, and it is possible to suppress impurities such as hydrogen or water that intrude from the outside. On the other hand, the insulating film 934 has high moisture permeability. Therefore, the insulating film 934 is disposed inside the sealing material 925, and is disposed on the insulating film 924. The sealing material 925 can suppress impurities such as hydrogen or water intruding from the outside, and can suppress fluctuations in electrical characteristics of the transistor 910 and the transistor 911.

In the liquid crystal display device, an optical member (optical substrate) such as a black matrix (light-shielding film), a polarizing member, a phase difference member, and an anti-reflection member is appropriately provided. For example, circular polarization using a polarizing substrate and a phase difference substrate can also be used. Further, as the light source, a backlight, a sidelight, or the like can also be used.

Further, since the transistor is easily damaged by static electricity or the like, it is preferable to provide a protection circuit for protecting the drive circuit. The protection circuit is preferably constructed using a non-linear element.

31A to 31C show an example in which a common connection portion (pad portion) electrically connected to the second electrode 931 provided on the substrate 906 is formed on the substrate 901 in the liquid crystal display device shown in FIG.

The common connection portion is disposed at a position overlapping with the sealing material for bonding the substrate 901 and the substrate 906, and is electrically connected to the second electrode 931 by the conductive particles contained in the sealing material. Alternatively, a common connection portion is provided at a position where the sealing material does not overlap (note a position other than the pixel portion), and a paste containing conductive particles other than the sealing material is separately disposed so as to overlap with the common connection portion, and The two electrodes 931 are electrically connected.

The right side of Fig. 31A is a cross-sectional view of the transistor 910 provided in the pixel portion, and the left side of Fig. 31A is a cross-sectional view of a common connection portion which can be formed by the same process as the transistor. The common connection portion shown in Fig. 31A corresponds to the cross section of I-J in the plan view of the common connection portion shown in Fig. 31B.

The common potential line 975 is provided on the gate insulating film 922 and is fabricated using the same material and process as the source electrode 971 or the gate electrode 973 of the transistor 910.

Further, the common potential line 975 is covered by the insulating film 924 and the insulating film 934, and the insulating film 924 and the insulating film 934 have a plurality of openings at positions overlapping the common potential line 975. The opening is fabricated using the same process as the contact hole, which connects one of the source electrode 971 and the drain electrode 973 of the transistor 910 with the first electrode 930.

Further, the common potential line 975 and the common electrode 977 are electrically connected to each other in an opening provided in the insulating film 924 and the insulating film 934. The common electrode 977 is provided on the insulating film 934 and is fabricated using the same material and process as the first electrode 930 connecting the terminal electrode 915 and the pixel portion.

In this manner, the common connection portion is manufactured in common with the process of the switching element of the pixel portion 902.

The common electrode 977 is an electrode that is in contact with the conductive particles included in the sealing material, and is electrically connected to the second electrode 931 of the substrate 906.

Further, as shown in FIG. 31C, the common potential line 985 can also be fabricated using the same material and process as the gate electrode of the transistor 910.

In the common connection portion shown in FIG. 31C, the common potential line 985 is disposed under the gate insulating film 922, the insulating film 924, and the insulating film 934, and the gate insulating film 922, the insulating film 924, and the insulating film 934 are overlapped in the common The potential line 985 has a plurality of openings at the location. The same process is used for the insulating film 924 and the insulating film by using a contact hole which connects one of the source electrode 971 and the gate electrode 973 of the transistor 910 and the first electrode 930. After the 934 is etched, the gate insulating film 922 is also selectively etched to form the opening.

Further, the common potential line 985 and the common electrode 987 are electrically connected to openings provided in the insulating film 922, the insulating film 924, and the insulating film 934. The common electrode 987 is provided on the insulating film 934 and is fabricated by the same material and process as the first electrode 930 connecting the terminal electrode 915 and the pixel portion.

As described above, by applying the transistor and the capacitor element described in the above embodiments, it is possible to provide a semiconductor device in which the aperture ratio is increased and the capacitor element having an increased charge capacity is increased. As a result, a semiconductor device excellent in display quality can be obtained.

In addition, since the oxygen defect of the oxide semiconductor film as the semiconductor film included in the transistor is reduced and impurities such as hydrogen are reduced, the semiconductor device of one embodiment of the present invention becomes a semiconductor device having excellent electrical characteristics.

Further, the present embodiment can be combined as appropriate with other embodiments shown in the present specification.

Embodiment 6

In the present embodiment, a configuration of an information processing device capable of processing and displaying video information to which a semiconductor device according to one embodiment of the present invention can be applied will be described with reference to FIGS. 32 and 33A1 to FIG. 33B2.

Specifically, the information processing apparatus having the first mode and the second mode will be described, and in the first mode, 30 Hz (30 per second) The frequency above the frequency, preferably 60 Hz (60 times per second) and below 960 Hz (960 times per second), outputs the G signal of the selected pixel, and in the second mode is 11.6 μHz ( The frequency of 1 or more times per day and less than 0.1 Hz (0.1 times per second) is preferably 0.28 mHz (1 time per hour) or less and less than 1 Hz (1 time per 1 second). Output G signal.

By displaying the still image by using the information processing apparatus of one embodiment of the present invention, the update rate can be set to be lower than 1 Hz, preferably 0.2 Hz or less, and the display of the user's eyes can be small, and the eyes of the user can be alleviated. Display of fatigue, display that does not burden the user's eyes. Further, the display image can be updated at the most appropriate frequency corresponding to the nature of the image displayed on the display portion. Specifically, it is possible to display a still image with less flicker by updating at a lower frequency than when the moving image is smoothly displayed. Plus, it also has the effect of reducing power consumption.

Fig. 32 is a block diagram showing the configuration of an information processing apparatus having a display function according to an embodiment of the present invention.

33A1 to 33B2 are block diagrams showing a configuration of a display unit provided in a display device according to an embodiment of the present invention.

The information processing device 600 having the display function described in the present embodiment includes a display device 640, an arithmetic device 620, and an input unit 500 (see FIG. 32).

The display device 640 has a display unit 630 and a control unit 610 (see FIG. 32). One image signal 625_V and one control signal 625_C may be supplied to the display device 640. The display device 640 can display image information on the display unit 630.

In addition to the grayscale information of the image (which may also be referred to as luminance information), the primary image signal 625_V includes, for example, chrominance information and the like.

The primary control signal 625_C includes, for example, a signal or the like for controlling the timing of the scanning operation of the display device 640, and the like.

Further, a power source potential or the like is supplied to the control unit 610 and the display unit 630 of the display device 640.

The control unit 610 has a function of controlling the display unit 630. For example, the control unit 610 generates a secondary video signal 615_V and/or a secondary control signal 615_C and the like.

The control unit 610 may be configured to include a polarity determination circuit. The polarity decision circuit can reverse the polarity of the signal for each frame.

The polarity determining circuit may have a function of notifying the timing of inverting the polarity of the secondary video signal 615_V, and the control unit 610 inverts the polarity of the secondary video signal 615_V based on the timing. Further, the control unit 610 may invert the polarity of the secondary video signal 615_V or may invert the polarity of the secondary video signal 615_V in the display unit 630 according to an instruction from the control unit 610.

Further, the polarity determining circuit may include a counter and a signal generating circuit and has a function of setting a timing for inverting the polarity of the secondary image signal 615_V using the synchronization signal.

Note that the counter has a function of counting the number of frames during the period using the pulse of the horizontal sync signal. In addition, the signal generating circuit has The function of notifying the control unit 610 of the timing of the polarity inversion of the secondary video signal 615_V. Thereby, the polarity of the secondary image signal 615_V can be inverted every several consecutive frame periods using the number information of the frame period obtained from the counter.

The secondary image signal 615_V can be made to include image information.

For example, the control unit 610 may generate the secondary video signal 615_V from the primary video signal 625_V and output the secondary video signal 615_V.

Further, the control unit 610 can generate a signal whose polarity is inverted for each frame as the secondary video signal 615_V with the difference between the primary video signal 625_V and the reference potential Vsc as the amplitude.

The secondary control signal 615_C may be included with a signal for controlling the first driving circuit (also referred to as G driving circuit 632) of the display portion 630 or a signal for controlling the second driving circuit (also referred to as S driving circuit 633).

For example, the control section 610 may generate the secondary control signal 615_C from the primary control signal 625_C including the synchronization signal of the vertical synchronization signal, the horizontal synchronization signal, and the like.

The secondary control signal 615_C includes, for example, an initial pulse signal SP, a latch signal LP, a pulse width control signal PWC, a clock signal CK, and the like.

Specifically, the secondary control signal 615_C may include the S-drive circuit initial pulse signal SP, S for controlling the operation of the S drive circuit 633, the drive circuit clock signal CK, the latch signal LP, and the like. another In addition, the G drive circuit initial pulse signal SP, the G drive circuit clock signal CK, the pulse width control signal PWC, and the like that control the operation of the G drive circuit 632 may be included.

The display portion 630 includes a pixel portion 631, a first driving circuit (also referred to as a G driving circuit 632), and a second driving circuit (also referred to as an S driving circuit 633).

The pixel portion 631 includes a plurality of pixels 631p whose display light does not include light having a wavelength shorter than 420 nm and which is set to have a sharpness of 150 ppi or more, and a wiring connecting the plurality of pixels. Each of the pixels 631p is connected to at least one scanning line G and one signal line S. Further, the type and number of wirings depend on the structure, number, and arrangement of the pixels 631p.

For example, when the pixel 631p is arranged in a matrix of x columns × y rows in the pixel portion 631, the signal line S1 to the signal line Sx and the scanning line G1 to the scanning line Gy are arranged in the pixel portion 631 (refer to FIG. 33A1). . A plurality of scanning lines (G1 to Gy) can supply G signals in rows. A plurality of signal lines (S1 to Sx) can supply S signals to a plurality of pixels.

The G drive circuit 632 can control the supply of the G signal 632_G to select the scan line G (refer to FIG. 32).

For example, the pixel portion 631 may be divided into a plurality of regions (specifically, divided into a first region 631a, a second region 631b, and a third region 631c) to be driven (see FIG. 33A2).

A plurality of pixels 631p; a plurality of scanning lines G for selecting the pixels 631p in rows; and a plurality of signal lines S for supplying the S signals 633_S to the selected pixels 631p may be provided in the respective areas.

Further, a plurality of G driving circuits may be provided (specifically, the first G driving circuit 632a, the second G driving circuit 632b, and the third G driving circuit 632c may be provided).

The G driving circuit can control the supply of the G signal 632_G to select the scanning lines G disposed in the respective regions (specifically, the first G driving circuit 632a selects the scanning lines G1 to Gj; the second G driving circuit 632b selects the scanning lines Gj+ 1 to G2j; and the third G drive circuit 632c selects the scan lines G2j+1 to Gy).

The G driving circuit outputs a first driving signal (also referred to as a G signal) 632_G of the selection pixel circuit 634 to the pixel circuit 634. The G drive circuit 632 includes a first mode and a second mode. In the first mode, the frequency is 30 Hz (30 times per second) or more, preferably 60 Hz (60 times per second) or more and less than 960 Hz. The frequency (960 times per second) outputs the G signal 632_G for selecting each scanning line to each scanning line, and is 11.6 μHz (1 time per day) or more and less than 0.1 Hz (every 1 second) in the second mode. The frequency of the clock is 0.1 times, preferably 0.28 mHz (1 time per hour) or more and less than 1 Hz (1 time per second), and the G signal 632_G is output to each scanning line.

The G drive circuit 632 can operate by switching between the first mode and the second mode. For example, the first mode and the second mode of the G drive circuit 632 can be switched by the G drive circuit start pulse included in the secondary control signal 615_C including the mode switching signal or the secondary control signal 615_C. Specifically, the output frequency of the G drive circuit start pulse outputted by the control unit 610 may be controlled.

The G signal 632_G is generated by the G drive circuit 632. The G signal 632_G is output to the pixel 631p in a row, and the pixel 631p is selected in a row.

The display unit 630 may have an S drive circuit 633. The S drive circuit generates a second drive signal (also referred to as an S signal 633_S) from the secondary image signal 615_V, and controls the supply of the S signal 633_S to the signal line S (specifically, the signal lines S1 to Sx).

The S signal 633_S includes grayscale information of the image and the like. The S signal 633_S is supplied to the pixel 631p selected by the G signal 632_G.

The pixel portion 631 includes a plurality of pixels 631p.

The pixel 631p includes a display element 635 and a pixel circuit 634 including the display element 635 (see FIG. 32).

The pixel circuit 634 holds the supplied S signal 633_S and displays a portion of the image information on the display element 635. In addition, a structure corresponding to the kind of the display element 635 or the driving method can be selected for the pixel circuit 634.

As an example of the pixel circuit 634, FIG. 33B1 shows a structure in which the liquid crystal element 635LC is applied to the display element 635.

The pixel circuit 634 includes a transistor 634t including a gate electrode to which the G signal 632_G is input and a first electrode to which the S signal is input, and a first electrode electrically connected to the second electrode of the transistor 634t and to be supplied with a common potential The liquid crystal element 635LC of the second electrode.

The pixel circuit 634 has a transistor 634t that controls the supply of the S signal 633_S to the display element 635.

The gate of the transistor 634t is connected to any one of the scanning line G1 to the scanning line Gy. One of the source and the drain of the transistor 634t is connected to any one of the signal line S1 to the signal line Sx, and the other of the source and the drain of the transistor 634t is connected to the first electrode of the display element 635.

The transistor 634t is used as a switching element that controls the input of the S signal 633_S to the pixel 631p in the pixel 631p. Further, a plurality of transistors may be used for the pixel 631p as one switching element. It is also possible to connect the above-mentioned plurality of transistors in parallel and use them as one switching element, or to connect them in series, or to combine parallel and series connection.

The pixel 631p may have other circuit elements such as a transistor, a diode, a resistor element, a capacitor element, an inductor, and the like in addition to the capacitor element 634c for maintaining the voltage between the first electrode and the second electrode of the liquid crystal element 635LC. . A specified common potential Vcom is applied to the second electrode of display element 635.

The capacitance of the capacitive element 634c can be appropriately adjusted. For example, in the second mode described later, in the case where the S signal 633_S is held for a long period of time (specifically, 1/60 sec or more), the capacitive element 634c is provided. Further, the capacitance of the pixel circuit 634 may be adjusted using a configuration other than the capacitive element 634c. Further, the capacitance element can be substantially formed by adopting a configuration in which the first electrode and the second electrode of the liquid crystal element 635LC are overlapped.

As another example of the pixel circuit, FIG. 33B2 shows a structure in which the EL element 635EL is applied to the display element 635.

The pixel circuit 634EL has a first transistor 634t_1 including: a gate electrode to which the G signal 632_G is input; a first electrode to which the S signal is input; and a first electrode electrically connected to the first electrode of the capacitive element 634c Two electrodes. In addition, the pixel circuit 634EL further has a second transistor 634t_2, the second transistor 634t_2 includes: a gate electrode electrically connected to the second electrode of the first transistor 634t_1; and a second electrode electrically connected to the second electrode of the capacitor element 634c An electrode; and a second electrode electrically connected to the first electrode of the EL element 635EL. Further, a power source potential is supplied to the second electrode of the capacitive element 634c and the first electrode of the second transistor 634t_2, and a common potential is supplied to the second electrode of the EL element 635EL. Note that the potential difference between the power source potential and the common potential is larger than the light emission start voltage of the EL element 635EL.

In the pixel circuit 634, the transistor 634t controls whether or not the potential of the signal line S is applied to the first electrode of the display element 635.

Further, a transistor using an oxide semiconductor as a transistor suitable for the display device of one embodiment of the present invention can be applied. For details of the transistor using an oxide semiconductor, the descriptions of the first embodiment and the second embodiment can be referred to.

The transistor using the oxide semiconductor film can make the leakage current (off-state current) between the source and the drain in the off state much lower than the conventional transistor using germanium. By using a transistor having a very small off-state current for the pixel portion of the display portion, it is possible to reduce the frame frequency while suppressing the occurrence of flicker.

As the display element 635, it is not limited to the liquid crystal element For the 635LC, for example, various display elements such as an OLED element that emits light by applying a voltage (Electroluminescence) or an electronic ink that uses electrophoresis can be applied.

For example, the transmittance of the polarized light of the liquid crystal element 635LC can be controlled by the potential of the S signal 633_S, whereby the gray scale can be displayed.

For example, when a transmissive liquid crystal element is used for the display element 635, the light supply portion 650 may be disposed on the display portion 630. The light supply unit 650 has a light source. The control unit 610 controls driving of the light source included in the light supply unit 650. The light supply portion 650 supplies light to the pixel portion 631 provided with the liquid crystal element and functions as a backlight.

As the light source of the light supply unit 650, a cold cathode fluorescent lamp, a light emitting diode (LED), an OLED element, or the like can be used.

In particular, it is preferable to adopt a structure in which the intensity of the blue light emitted from the light source is weaker than the intensity of the light of the other colors. This is because the blue-emitting light included in the light emitted by the light source reaches the retina without being absorbed by the cornea or lens of the eye, so that the long-term negative effect on the retina can be reduced (for example, age-related) Macular degeneration, etc.) or the negative effects of Circadian rhythm until late exposure to blue light. Specifically, the light source is preferably a light source that emits light that does not include light having a wavelength of 400 nm or less, preferably 420 nm or less, more preferably 440 nm or less (also referred to as UVA).

Note that the pixel in the semiconductor device of one embodiment of the present invention is characterized in that light having the above wavelength is absorbed and is not easily penetrated Over. Therefore, by using the semiconductor device of one embodiment of the present invention, even if a light source that emits light having the above-described wavelength is used, light having the above-described wavelength can be reduced or interrupted.

The arithmetic device 620 generates a primary image signal 625_V and a primary control signal 625_C including a mode switching signal.

The mode switching signal can be generated, for example, by an instruction of a user of the information processing device 600.

The user of the information processing device 600 can use the input unit 500 to issue an instruction to switch the display. It is also possible to supply the image switching signal 500_C to the arithmetic device 620, and the arithmetic device 620 outputs the structure of the primary control signal 625_C including the mode switching signal.

The primary control signal 625_C including the mode switching signal is supplied to the control section 610 of the display device 640, and the control section outputs the secondary control signal 615_C including the mode switching signal.

For example, when the secondary control signal 615_C including the mode switching signal that switches the second mode to the first mode is supplied to the G driving circuit 632, the G driving circuit 632 switches from the second mode to the first mode. Further, the G drive circuit 632 outputs the G signal one frame or more, and then switches to the second mode.

Specifically, a configuration in which the image switching signal 500_C is output to the arithmetic device 620 when the input unit 500 detects the page turning operation can also be employed.

The arithmetic device 620 generates a primary image signal 625_V including a page turning operation, and outputs a pattern including the primary image signal 625_V The primary control signal 625_C of the switching signal.

The control unit 610 that supplies the primary image signal 625_V and the primary control signal 625_C supplies a secondary control signal 615_C including a mode switching signal and a secondary image signal 615_V including a page turning operation.

The G drive circuit 632 supplied with the secondary control signal 615_C including the mode switching signal is switched from the second mode to the first mode, and outputs the G signal 632_G at a high frequency.

The S drive circuit 633 supplied with the secondary image signal 615_V including the page turning operation outputs the S signal 633_S generated by the secondary image signal 615_V to the pixel circuit 634.

Thereby, the pixel 631p can overwrite a plurality of frame images including the page turning operation at a high frequency. As a result, the secondary image signal 615_V including the page turning operation can be smoothly displayed.

It is also possible to adopt a configuration in which the arithmetic unit 620 discriminates whether the primary video signal 625_V outputted to the display unit 630 is a motion picture or a still picture, and outputs a primary control signal 625_C including a mode switching signal based on the discrimination result.

Specifically, the following configuration may also be adopted: when the primary image signal 625_V is a motion image, the arithmetic device 620 outputs a switching signal for selecting the first mode, and when the primary image signal 625_V is a still image, the arithmetic device 620 outputs the selection. The switching signal of the second mode.

In addition, as a method for the arithmetic device 620 to distinguish whether it is a moving image or a still image, there is a method of: between a signal of a frame included in the primary image signal 625_V and a signal of the frame before and after the frame When the difference is larger than the preset difference, it is discriminated as a motion picture, and when the difference between the signal of one frame included in the primary image signal 625_V and the signal of the frame before and after the frame is equal to or smaller than a preset difference, the discrimination is performed. Is a still image.

When the control unit 610 switches the operation mode of the G drive circuit from one mode to another mode (for example, when switching from the second mode to the first mode), the G drive circuit may also output the G signal 632_G more than once a predetermined number of times. After that, switch to another mode.

As the input unit 500, a touch panel, a touch panel, a mouse, a joystick, a trackball, a data glove, a camera, or the like can be used. The arithmetic device 620 can correlate the electrical signals input from the input unit 500 and the coordinates of the display portion with each other. Thereby, the user can input an instruction for processing the information displayed on the display section.

As the information input by the user from the input unit 500, for example, a drag command for changing the display position of the image displayed on the display unit, a slide command for turning the display image to the next image, and a reel-like image are sequentially displayed. Scroll instruction; an instruction to select a specific image; a zoom instruction to change the display size of the image; and an instruction to input a handwritten text.

Illuminance refers to the amount of light incident on a unit area per unit time of the illuminated surface, which includes the spectral sensitivity of the eye.

Note that this embodiment can be combined as appropriate with other embodiments shown in the present specification.

Embodiment 7

In the present embodiment, an information processing method of an information processing device using a semiconductor device according to one embodiment of the present invention will be described with reference to FIGS. 34A and 34B.

Specifically, a method of generating an image on the display unit of the information processing device using the semiconductor device of one embodiment of the present invention will be described. In particular, a method of switching between images in which the user's eyes are less irritated, a method of switching images that reduce eye strain of the user, and an eye band that does not give the user's eyes when the image displayed on the display unit is switched to another image will be described. The method of switching the image to be burdened.

34A and 34B are block diagrams showing the configuration of an information processing apparatus of a semiconductor device to which one embodiment of the present invention is applied, and a schematic diagram for explaining image data.

In one aspect of the present invention, a method of smoothly rewriting a display image on a display unit of the information processing device will be described.

Thereby, it is possible to reduce the burden on the eyes of the user when switching the display. As a result, it is possible to provide a novel information processing method capable of displaying an image including information processed by the arithmetic unit in such a manner that the eye stimulation is small.

When the image is quickly switched and displayed, it may cause eye strain to the user. For example, it includes continuously switching between moving images of different scenes and switching between different still images.

When switching between different images for display, it is preferable to switch the images slowly and quietly (naturally) and display them without Switch the display.

For example, when the display is switched from the first still image to the second still image, it is preferable to insert a moving image that displays the first still image or/and a second between the first still image and the second still image. A moving image in which the still image is faded in. In addition, it is also possible to insert a motion image in which two images are overlapped while the first still image fades out, and the second still image is faded in (also referred to as alternating fade), and the first still image can be inserted and displayed. Two dynamic images of still images (also known as image distortion).

In addition, the second still image data may be displayed at a low update rate after the first still image data is displayed at a low update rate, and then the image used to switch the image is displayed at a high update rate.

An example of a method of switching the different images A and B from each other will be described below.

FIG. 34A is a block diagram showing a configuration of a display unit capable of performing a video switching operation. The display unit illustrated in FIG. 34A includes a calculation unit 701, a storage unit 702, a control unit 703, and a display unit 704.

In the first step, the calculation unit 701 stores the respective pieces of the image A and the image B from the external storage unit and the like in the storage unit 702.

In the second step, the calculation unit 701 sequentially generates new video data using the respective image data of the video A and the video B based on the value of the preset number of divisions.

In the third step, the generated image data is output to the control unit 703. The control unit 703 displays the input image data in the display Showing portion 704.

FIG. 34B is a schematic diagram for explaining image data generated when the image is gradually switched from the image A to the image B.

FIG. 34B shows a case where N (N is a natural number) image data is generated from the image A to the image B, and f (f is a natural number) frame period is displayed for each of the image data. Thus, the period from the video A to the video B is an f×N frame.

Here, it is preferable that the user can freely set parameters such as N and f described above. The calculation unit 701 acquires these parameters in advance, and generates image data based on the parameters.

The i-th generated image data (i is an integer of 1 or more and N or less) can be generated by weighting the image data of the image A and the image data of the image B, respectively, and adding the image data together. For example, in a certain pixel, when the brightness (gray scale) when the image A is displayed is a, and when the brightness (gray scale) when the image B is displayed is b, the pixel of the image data generated by the ith is displayed. The luminance (gray scale) c is the value shown in Formula 1. Further, the gray scale refers to the level of shading displayed on the display unit. An image with only two levels of white and black can also be said to have two grayscale images. For example, a display portion of a conventional personal computer has sub-pixels that display red, green, and blue. A signal for displaying 256 levels of shading is input to each sub-pixel.

By using the image data generated by this method, the image A is switched to the image B, so that the discontinuous image can be switched slowly (quietly) and naturally.

Note that as for Equation 1, in all pixels, when a=0, it is equivalent to gradually switching from the black image to the fade in of the image B. Further, in all the pixels, when b=0, it is equivalent to gradually switching from the image A to the fade-out of the black image.

Although the method of temporarily overlapping two images and switching the images has been described in the above description, a method of not repeating the images may be employed.

In the case where the two images are not overlapped, it is also possible to insert a black image therebetween when the image A is switched to the image B. In this case, the image switching method may be employed when migrating from the image A to the black image, from the black image to the image B, or both. Further, as the image inserted between the image A and the image B, not only a black image but also a monochrome image such as a white image or a multicolor image different from the image A and the image B may be used.

By inserting other images, such as monochrome images, such as black images, between the image A and the image B, the user can more naturally feel the timing of the image switching, thereby switching the image in a manner that does not make the user feel uncomfortable. .

This embodiment can be combined as appropriate with other embodiments shown in the present specification.

Embodiment 8

In the present embodiment, a configuration of an information processing apparatus using a semiconductor device according to one embodiment of the present invention will be described with reference to FIGS. 35A1 to 35B2 and FIG.

35A1 to 35B2 are diagrams for explaining the effects of the information processing apparatus.

Figure 36 is a block diagram showing the structure of an information processing apparatus.

Eye fatigue has two kinds of fatigue: nerve fatigue and muscle fatigue. 35A1 and 35A2 show schematic diagrams illustrating eye fatigue.

Nerve fatigue refers to the fact that the brightness or the brain is reflected by the retina, the optic nerve or the brain of the eye due to continuous viewing of the light or the flickering image emitted by the display portion for a long time. The phenomenon in which the display portion of the fluorescent lamp or the conventional display device is slightly extinguished is called flicker, and the flicker causes nerve fatigue.

Muscle fatigue is caused by excessive use of the ciliary muscles used to adjust the focus.

Fig. 35A1 is a schematic view showing the display of a conventional display unit. The conventional display unit performs image rewriting 60 times in one second. Watching this screen for a long time may cause eye fatigue due to the user's retina, optic nerve or brain.

Further, as shown in FIG. 35A2, when the size of one pixel is large (for example, when the resolution is lower than 150 ppi), the outline of characters or the like displayed on the display portion is blurred. For a long time, the text of the outline displayed on the liquid crystal display device is blurred, that is, the ciliary muscle is adjusted for focusing. The point is constantly moving and in a state of constant tension, which may cause a burden on the eyes.

In addition, methods for quantitatively measuring eye fatigue have been studied. For example, as an evaluation index of nerve fatigue, a critical flicker (fusion) frequency (CFF: Critical Flicker (Fusion) Frequency) or the like is known. As an evaluation index of muscle fatigue, adjustment time, adjustment of a near point distance, and the like are known.

In addition to the above, as a method for evaluating eye fatigue, brain wave measurement, temperature map method, measurement of the number of blinks, evaluation of the amount of tears, evaluation of the contraction reaction rate of the pupil, and questionnaire for investigating the subjective symptoms are known.

In order to solve the above problems, one aspect of the present invention focuses on the illumination of the work environment and the gray tone of the background of the image information displayed by the display device. In the embodiments described below, one embodiment of the present invention created by focusing on the illuminance information of the environment and the gray tone information of the background of the image information is included.

The method for processing and displaying image information in one aspect of the present invention includes the steps of: obtaining illuminance information of the environment and gray tone information of the background of the image information displayed by the display unit; and displaying the image information by using the information In the step of displaying the plurality of pixels, the plurality of pixels do not include light having a wavelength shorter than 420 nm and are set with a sharpness of 150 ppi or more. Thereby, the image information can be displayed with brightness suitable for ambient illumination. As a result, it is possible to provide processing of novel image information capable of performing image information processing and displaying less eye irritation. And display method.

Fig. 36 shows an example of a block diagram of the information processing apparatus. The information processing device is an information processing device that can process and display image information of one embodiment of the present invention.

The information processing device 330 includes a calculation unit 311, a storage unit 312, and a transmission channel 314. The calculation unit 311, the storage unit 312, and the input/output interface 315 are connected to each other by the transmission channel 314 to transmit information. Note that the above structure cannot be clearly separated, and sometimes one structure doubles as part of other structures or contains other structures. For example, the touch panel is both a display portion and an input unit.

Input/output device 320 is coupled to transmit channel 314 via input/output interface 315. The input/output device 320 is a device for inputting information from the outside of the arithmetic device 310 or outputting information to the outside of the arithmetic device 310.

As an example of the input/output device 320, a communication device, a network interconnection device, an external memory that can be written, such as a hard disk or a removable memory can be cited.

Examples of the input unit 321 include a peripheral device such as a keyboard, a mouse, or a touch panel; a camera such as a digital camera or a digital camera; and a read-only external memory unit such as a scanner, a CDROM, and a DVDROM. For example, the user of the information processing device 330 can input a page turning instruction or the like from the input unit 321.

As the output device, in addition to the display unit 322, a speaker, a printer, or the like can be connected.

The information processing device 330 according to an aspect of the present invention has a display unit 322. In particular, in the display unit 322, the display light does not include light having a wavelength shorter than 420 nm, and preferably does not include light having a wavelength shorter than 440 nm. Further, it is preferable to provide a plurality of pixels having a definition of 150 ppi or more, more preferably 200 ppi or more, in the display area. Thereby, it is possible to perform a display with less stimulation of the eyes. Note that in the present specification, the display light refers to light that is emitted or reflected to the user by the display unit of the information processing device in order to display an image.

The display light of the display portion according to one aspect of the present invention reaches the retina because it is not absorbed by the cornea or the lens of the eye, and thus does not include light having a long-term influence on the retina or having a bad influence on the circadian rhythm. Specifically, the light for displaying an image does not include light having a wavelength of 400 nm or less, preferably 420 nm or less, more preferably 440 nm or less (also referred to as UVA).

The information processing device 330 according to an aspect of the present invention can use the semiconductor device of one embodiment of the present invention. The pixel in the semiconductor device is characterized in that light having the above wavelength is absorbed and is not easily transmitted. Therefore, by using the semiconductor device of one embodiment of the present invention, even if a light source that emits light having the above-described wavelength is used, light having the above-described wavelength can be reduced or interrupted.

Further, the definition of the pixel included in the display unit according to the aspect of the present invention is 150 ppi or more, preferably 200 ppi or more, and the size of one pixel is small. Thereby, the muscle fatigue of the user's eyes can be alleviated.

35B1 and 35B2 are diagrams for explaining the effect of reducing eye strain in the information processing apparatus of one embodiment of the present invention.

The information processing apparatus of one embodiment of the present invention can change the frequency of the signal outputting the selected pixel. In particular, by using a transistor having a very small off-state current for the pixel portion of the display portion, it is possible to reduce the frame frequency while suppressing the occurrence of flicker. For example, the image can be rewritten in a manner of once every 5 seconds, so that the same image can be viewed, and the flicker of the screen perceived by the user can be reduced. Thereby, the stimulation of the retina, nerves, or brain of the user's eyes is reduced, thereby reducing nerve fatigue (see FIG. 35B1).

Further, as the transistor having a very small off-state current, for example, a transistor using an oxide semiconductor, in particular, a transistor using CAAC-OS is preferable.

The information processing apparatus according to an aspect of the present invention has a small size of one pixel. Specifically, a high-definition display having a resolution of 150 ppi or more, preferably 200 ppi or more can be performed. The outline of the image can be displayed clearly or meticulously and smoothly. Thereby, the focus adjustment of the ciliary muscle is facilitated, and the muscle fatigue of the user can be alleviated (refer to FIG. 35B2). Note that sharpness can be expressed using pixel density (ppi: pixel per inch). The pixel density is the number of pixels per inch. In addition, a pixel is a unit constituting an image.

Note that this embodiment can be combined as appropriate with other embodiments shown in the present specification.

Embodiment 9

The semiconductor device of one embodiment of the present invention can be applied to various electronic devices (including game machines). Examples of the electronic device include a television set, a display for a computer, a digital camera, a digital camera, a digital photo frame, a mobile phone, a game machine, a portable game machine, a portable information terminal, an audio reproduction device, and a game machine. (pachinko machine or slot machine, etc.). 37A to 38B show an example of the above electronic device.

Fig. 37A shows a table having a display portion. In the table 9000, a display portion 9003 is incorporated in the casing 9001, and an image can be displayed by the display portion 9003. In addition, the structure in which the outer casing 9001 is supported by the four legs 9002 is shown. In addition, the housing 9001 has a power supply line 9005 for supplying electric power.

The semiconductor device shown in any of the above embodiments can be used for the display portion 9003. Therefore, the display quality of the display portion 9003 can be improved.

The display unit 9003 has a touch panel input function, and can perform screen operation or information input by pressing the display button 9004 displayed on the display portion 9003 of the table 9000 with a finger or the like, and the display portion 9003 can also be used as a control device, that is, Other home appliances are controlled by screen operations by having a function of being able to communicate with other home appliances or a function of controlling other home appliances. For example, the display portion 9003 can have a touch screen input function by using a semiconductor device having a touch sensor function or an image sensor function.

Further, the screen of the display portion 9003 can be stood upright perpendicular to the floor by the hinge provided on the casing 9001, and the table can also be used as a television. Although the space for free use is small when a large-screen television is installed in a small room, if the display portion is installed in the table, the space of the room can be effectively utilized.

Fig. 37B shows a television set. In the television set 9100, the housing 9101 is assembled with the display portion 9103, and an image can be displayed by the display portion 9103. Further, the structure in which the housing 9101 is supported by the bracket 9105 is shown here.

The operation of the television set 9100 can be performed by using an operation switch provided in the casing 9101 and a separately provided remote controller 9110. By using the operation keys 9109 provided in the remote controller 9110, the operation of the channel and the volume can be performed, and the image displayed on the display unit 9103 can be operated. Further, a configuration in which the display unit 9107 that displays information output from the remote controller is provided in the remote controller 9110 may be employed.

The television set 9100 shown in FIG. 37B includes a receiver, a communication unit, and the like. The television set 9100 can receive general television broadcasts using a receiver. Furthermore, the television set 9100 can be connected to a wired or wireless communication network by means of a communication unit, and can also be unidirectional (from sender to receiver) or bidirectional (between sender and receiver or receiver). ) Information communication.

The semiconductor device shown in any of the above embodiments can be used for the display unit 9103 and the display unit 9107. Therefore, the display quality of the television can be improved.

37C shows a computer 9200 including a main body 9201, a housing 9202, a display portion 9203, a keyboard 9204, an external connection port 9205, a pointing device 9206, and the like.

The semiconductor device shown in any of the above embodiments can be used for the display portion 9203. Therefore, the display quality of the computer 9200 can be improved.

The display portion 9203 has a touch panel input function, and can perform screen operation or information input by pressing a display button in the display portion 9203 with a finger or the like. In addition, you can use the keyboard or audio to enter information.

38A and 38B are tablet terminals that can be folded. 38A is a tablet terminal in an open state, and includes a housing 9630, a display portion 9631a, a display portion 9631b, a display mode changeover switch 9034, a power switch 9035, a power saving mode changeover switch 9036, a clip 9033, and an operation switch 9038.

The semiconductor device shown in any of the above embodiments can be used for the display portion 9631a and the display portion 9631b. Therefore, the display quality of the tablet terminal can be improved.

In the display portion 9631a, a part thereof can be used as the area 9632a of the touch panel, and the material can be input by pressing the displayed operation key 9638. Further, as an example, it is shown here that half of the display portion 9631a has only the function of display, and the other half has the function of the touch panel, but is not limited to this structure. It is also possible to adopt a configuration in which the entire area of the display portion 9631a has the function of the touch panel. For example, the entire surface of the display portion 9631a can be displayed as a keyboard button to use it as a touch The panel is used, and the display portion 9631b is used as a display screen.

Further, similarly to the display portion 9631a, the display portion 9631b can be used as a region 9632b of the touch panel. Further, the keyboard button can be displayed on the display portion 9631b by pressing the display keyboard of the touch panel to display the position of the switching button 9639 using a finger or a stylus.

In addition, the touch panel input may be simultaneously performed on the touch panel area 9632a and the touch panel area 9632b.

Further, the display mode changeover switch 9034 can switch between display directions such as portrait display and landscape display, and switching between black and white display, color display, and the like. The power saving mode changeover switch 9036 can set the displayed brightness to the most suitable brightness based on the amount of external light used during use detected by the photosensor built into the tablet terminal. In addition to the photo sensor, the tablet terminal may include other detecting devices such as a gyroscope and an acceleration sensor that detect the inclination.

Further, FIG. 38A shows an example in which the display area of the display portion 9631b is the same as the display area of the display portion 9631a, but the present invention is not limited thereto, and the size of one and the other may be different, and their display qualities may be different. For example, one of the display portion 9631a and the display portion 9631b can perform a higher-definition display than the other.

FIG. 38B is a tablet terminal in a closed state, and a solar battery 9633 and a charge and discharge control circuit 9634 may be included in the housing 9630. Further, in FIG. 38B, a junction having a battery 9635 and a DCDC converter 9636 is shown as an example of the charge and discharge control circuit 9634. Structure.

In addition, the tablet terminal can be folded so that the housing 9630 can be closed when not in use. Therefore, the display portion 9631a and the display portion 9631b can be protected, and a tablet terminal having excellent durability and high reliability from the viewpoint of long-term use can be provided.

In addition, the tablet terminal shown in FIG. 38A and FIG. 38B may further have the following functions: displaying various kinds of information (still image, motion picture, text image, etc.); displaying the calendar, date, time, and the like on the display unit; A touch input for displaying or editing information displayed on the display unit; controlling processing by various software (programs) and the like.

By using the solar battery 9633 mounted on the surface of the tablet terminal, power can be supplied to the touch panel, the display portion, the video signal processing portion, and the like. Note that the solar cell 9633 can be disposed on one or both sides of the outer casing 9630, so that the charging of the battery 9635 can be performed efficiently. Further, when a lithium ion battery is used as the battery 9635, there is an advantage that downsizing or the like can be achieved.

Further, the configuration and operation of the charge and discharge control circuit 9634 shown in Fig. 38B will be described with reference to the block diagrams shown in Figs. 39A to 39C. 39A shows a solar battery 9633, a battery 9635, a DCDC converter 9636, a DCDC converter 9637, switches SW1 to SW3, and a load (display portion 9631, etc.), a battery 9635, a DCDC converter 9636, a DCDC converter 9637, and a switch SW1 to SW3 corresponds to the charge and discharge control circuit 9634 shown in Fig. 38B.

First, when using solar cells 9633 to generate electricity, An example of work. The power generated by the solar cell is boosted or stepped down using a DCDC converter 9636 to become a voltage for charging the battery 9635. When the load (display portion 9631 or the like) is operated by the electric power from the solar battery 9633, the switch SW1 is turned on, and the DCDC converter 9637 is used to boost or step down the load to the load (the display portion 9631 or the like). Voltage. In addition, when power supply to the load (display portion 9631 or the like) is not performed, a configuration may be employed in which SW1 is turned off and SW2 is turned on to charge the battery 9635.

When the power supply to the load (display portion 9631 or the like) is always performed, as shown in FIG. 39B, the configuration in which the switch SW1 is omitted may be employed.

Further, when the appropriate range of the voltage supplied to the load is the same as the voltage of the battery 9635, as shown in FIG. 39C, a configuration in which the DCDC converter 9637 is also omitted may be employed.

Note that the solar battery 9633 is shown as an example of the power generation unit, but the battery is not limited thereto, and other power generation units such as a piezoelectric element or a thermoelectric conversion element (Peltier element) may be used for the battery. 9635 charging. For example, a non-contact power transmission module that transmits and receives power by wireless (contactless) to perform charging, or a combination of other charging units for charging may be employed.

The structure, method, and the like described in the present embodiment can be implemented in appropriate combination with the structures, methods, and the like described in the other embodiments.

102‧‧‧Substrate

103‧‧‧Optoelectronics

105‧‧‧Capacitive components

107‧‧‧ scan line

109‧‧‧ signal line

110‧‧‧Base insulating film

111‧‧‧Semiconductor film

113‧‧‧Electrical film

115‧‧‧ capacitance line

119‧‧‧Semiconductor film

121‧‧‧pixel electrode

127‧‧‧gate insulating film

129‧‧‧Insulation film

131‧‧‧Insulation film

132‧‧‧Insulation film

223‧‧‧Optoelectronics

227‧‧‧gate electrode

229‧‧‧Wiring

231‧‧‧Semiconductor film

233‧‧‧Wiring

241‧‧‧Electrical film

Claims (21)

A semiconductor device comprising: an oxide crystal comprising: an oxide semiconductor layer on a first insulating film; a source electrode layer and a drain electrode layer electrically connected to the oxide semiconductor layer; the oxide semiconductor layer, a source electrode layer and a second insulating film on the gate electrode layer; and a gate electrode layer on the oxide semiconductor layer via the second insulating film; and a capacitor element including: a first electrode of the oxide semiconductor layer in the same layer, the first electrode is located on the first insulating film; a transparent conductive film serving as a second electrode of the capacitor element, the transparent conductive film overlapping the first electrode; And a dielectric between the first electrode and the second electrode. The semiconductor device according to claim 1, further comprising: a wiring electrically connected to the first electrode, wherein the source electrode layer, the drain electrode layer, and the wiring are formed using the same material. The semiconductor device of claim 1, further comprising: the second insulating film and a third insulating film on the gate electrode layer; a fourth insulating film on the third insulating film, wherein the second insulating film, the third insulating film, and the fourth insulating film overlap the first electrode, and the dielectric includes the second insulating film, the third An insulating film and the fourth insulating film. The semiconductor device according to claim 3, wherein the third insulating film has an oxidized insulating material comprising a metal oxide selected from the group consisting of cerium oxide, cerium oxynitride, aluminum oxide, cerium oxide, gallium oxide, and Ga-Zn-based metal oxide. Single layer structure or laminate structure. The semiconductor device according to claim 3, wherein the fourth insulating film has a single layer structure or a stacked structure including a nitride insulating material selected from the group consisting of bismuth oxynitride, tantalum nitride, aluminum nitride, and aluminum oxynitride. . The semiconductor device of claim 1, further comprising: the second insulating film and a third insulating film on the gate electrode layer, the third insulating film being in contact with the first electrode; and the third insulating film a fourth insulating film, wherein the third insulating film and the fourth insulating film overlap the first electrode, and the dielectric includes the third insulating film and the fourth insulating film. The semiconductor device of claim 1, further comprising: the second insulating film and a third insulating film on the gate electrode layer; a fourth insulating film on the third insulating film, the fourth insulating film being in contact with the first electrode, wherein the fourth insulating film overlaps the first electrode, and the dielectric includes the fourth insulating film. The semiconductor device according to claim 1, further comprising a nitride insulating film between the first insulating film and the first electrode, the nitride insulating film being in contact with the first electrode. The semiconductor device according to claim 1, wherein the first electrode includes a metal element included in the oxide semiconductor layer. The semiconductor device according to claim 1, wherein the first electrode comprises one or more elements selected from the group consisting of hydrogen, boron, nitrogen, fluorine, aluminum, phosphorus, arsenic, indium, tin, antimony, and a rare gas element. The semiconductor device according to claim 1, wherein the oxide semiconductor layer has an energy gap of 2.0 eV or more. The semiconductor device according to claim 1, wherein the transparent conductive film is electrically connected to one of the source electrode layer and the gate electrode layer. A method of fabricating a semiconductor device, comprising the steps of: forming an oxide semiconductor film on a first insulating film; forming a first oxide semiconductor layer and a second oxide semiconductor layer by patterning the oxide semiconductor film; Forming a conductive film on the first oxide semiconductor layer and the second oxide semiconductor layer; Forming the conductive film to form a source electrode layer and a drain electrode layer electrically connected to the first oxide semiconductor layer and a wiring electrically connected to the second oxide semiconductor layer; at the first insulation Forming a second insulating film on the film, the first oxide semiconductor layer, the second oxide semiconductor layer, the source electrode layer, the gate electrode layer, and the wiring; forming the second insulating film and the first via a gate electrode layer in which an oxide semiconductor layer overlaps; a third insulating film is formed on the second insulating film and the gate electrode layer; a fourth insulating film is formed on the third insulating film; and the second insulating film is formed on the second insulating film An opening reaching the source electrode layer or the drain electrode layer is formed in the third insulating film and the fourth insulating film; and the opening portion and the source electrode layer are formed on the fourth insulating film Or a light-transmitting conductive film electrically connected to the drain electrode layer, wherein the capacitor element includes a first electrode formed of the second oxide semiconductor layer and the transparent conductive film serving as a second electrode of the capacitor element. The manufacturing method according to claim 13, wherein the second insulating film, the third insulating film, and the fourth insulating film are used as a dielectric of the capacitive element. The manufacturing method of claim 13, further comprising the step of etching a portion of the second insulating film overlapping the second oxide semiconductor layer to make the third insulating film and the fourth insulating film Used as a dielectric for the capacitive element. The manufacturing method of claim 13, further comprising the steps of: a portion of the second insulating film overlapping the second oxide semiconductor layer and the third insulating film overlapping the second oxide semiconductor layer A portion of the etching is performed so that the fourth insulating film serves as a dielectric of the capacitive element. The manufacturing method according to claim 13, wherein the first oxide semiconductor layer and the second oxide semiconductor layer have an energy gap of 2.0 eV or more. The manufacturing method of claim 13, further comprising the step of: adding, to the second oxide semiconductor layer, a component selected from the group consisting of hydrogen, boron, nitrogen, fluorine, aluminum, phosphorus, arsenic, indium, tin, antimony, and rare gas One or more of the dopants. The manufacturing method according to claim 13, wherein the third insulating film has an oxidizing insulating material comprising a metal oxide selected from the group consisting of cerium oxide, cerium oxynitride, aluminum oxide, cerium oxide, gallium oxide, and Ga-Zn-based metal oxide. Single layer structure or laminate structure. The manufacturing method according to claim 13, wherein the fourth insulating film has a single layer structure or a laminated structure including a nitride insulating material selected from the group consisting of bismuth oxynitride, tantalum nitride, aluminum nitride, and aluminum oxynitride. . According to the manufacturing method of claim 13 of the patent application, the following steps are also included: A nitride insulating film including hydrogen is formed before the oxide semiconductor film is formed, wherein the second oxide semiconductor layer overlaps the nitride insulating film.